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1.1     ! maekawa     1: C RCS $Id: gnuplot.doc,v 1.64 1998/06/18 14:59:14 ddenholm Exp $
        !             2: C 3 December 1998
        !             3: C Copyright (C) 1986 - 1993, 1998   Thomas Williams, Colin Kelley
        !             4: C
        !             5: ^ <h2> An Interactive Plotting Program </h2><p>
        !             6: ^ <h2>  Thomas Williams & Colin Kelley</h2><p>
        !             7: ^ <h2>   Version 3.7 organized by: David Denholm </h2><p>
        !             8: ^ <h2>Major contributors (alphabetic order):</h2>
        !             9: ^<ul><h3>
        !            10: ^<li>  Hans-Bernhard Broeker
        !            11: ^<li>  John Campbell
        !            12: ^<li>  Robert Cunningham
        !            13: ^<li>  David Denholm
        !            14: ^<li>  Gershon Elber
        !            15: ^<li>  Roger Fearick
        !            16: ^<li>  Carsten Grammes
        !            17: ^<li>  Lucas Hart
        !            18: ^<li>  Lars Hecking
        !            19: ^<li>  Thomas Koenig
        !            20: ^<li>  David Kotz
        !            21: ^<li>  Ed Kubaitis
        !            22: ^<li>  Russell Lang
        !            23: ^<li>  Alexander Lehmann
        !            24: ^<li>  Alexander Mai
        !            25: ^<li>  Carsten Steger
        !            26: ^<li>  Tom Tkacik
        !            27: ^<li>  Jos Van der Woude
        !            28: ^<li>  James R. Van Zandt
        !            29: ^<li>  Alex Woo
        !            30: ^</h3></ul> <p>
        !            31: ^<h2>  Copyright (C) 1986 - 1993, 1998   Thomas Williams, Colin Kelley<p>
        !            32: ^   Mailing list for comments: info-gnuplot@dartmouth.edu <p>
        !            33: ^   Mailing list for bug reports: bug-gnuplot@dartmouth.edu<p>
        !            34: ^</h2><p>
        !            35: ^<h3> This manual was prepared by Dick Crawford</h3><p>
        !            36: ^<h3> 3 December 1998</h3><p>
        !            37: ^<hr>
        !            38: 1 gnuplot
        !            39: 2 Copyright
        !            40: ?copyright
        !            41: ?license
        !            42:        Copyright (C) 1986 - 1993, 1998   Thomas Williams, Colin Kelley
        !            43:
        !            44:  Permission to use, copy, and distribute this software and its
        !            45:  documentation for any purpose with or without fee is hereby granted,
        !            46:  provided that the above copyright notice appear in all copies and
        !            47:  that both that copyright notice and this permission notice appear
        !            48:  in supporting documentation.
        !            49:
        !            50:  Permission to modify the software is granted, but not the right to
        !            51:  distribute the complete modified source code.  Modifications are to
        !            52:  be distributed as patches to the released version.  Permission to
        !            53:  distribute binaries produced by compiling modified sources is granted,
        !            54:  provided you
        !            55:    1. distribute the corresponding source modifications from the
        !            56:     released version in the form of a patch file along with the binaries,
        !            57:    2. add special version identification to distinguish your version
        !            58:     in addition to the base release version number,
        !            59:    3. provide your name and address as the primary contact for the
        !            60:     support of your modified version, and
        !            61:    4. retain our contact information in regard to use of the base
        !            62:     software.
        !            63:  Permission to distribute the released version of the source code along
        !            64:  with corresponding source modifications in the form of a patch file is
        !            65:  granted with same provisions 2 through 4 for binary distributions.
        !            66:
        !            67:  This software is provided "as is" without express or implied warranty
        !            68:  to the extent permitted by applicable law.
        !            69:
        !            70:
        !            71:        AUTHORS
        !            72:
        !            73:        Original Software:
        !            74:           Thomas Williams,  Colin Kelley.
        !            75:
        !            76:        Gnuplot 2.0 additions:
        !            77:           Russell Lang, Dave Kotz, John Campbell.
        !            78:
        !            79:        Gnuplot 3.0 additions:
        !            80:           Gershon Elber and many others.
        !            81: 2 Introduction
        !            82: ?introduction
        !            83: ?
        !            84:  `gnuplot` is a command-driven interactive function and data plotting program.
        !            85:  It is case sensitive (commands and function names written in lowercase are
        !            86:  not the same as those written in CAPS).  All command names may be abbreviated
        !            87:  as long as the abbreviation is not ambiguous.  Any number of commands may
        !            88:  appear on a line (with the exception that `load` or `call` must be the final
        !            89:  command), separated by semicolons (;).  Strings are indicated with quotes.
        !            90:  They may be either single or double quotation marks, e.g.,
        !            91:
        !            92:        load "filename"
        !            93:        cd 'dir'
        !            94:
        !            95:  although there are some subtle differences (see `syntax` for more details).
        !            96:
        !            97:  Any command-line arguments are assumed to be names of files containing
        !            98:  `gnuplot` commands, with the exception of standard X11 arguments, which are
        !            99:  processed first.  Each file is loaded with the `load` command, in the order
        !           100:  specified.  `gnuplot` exits after the last file is processed.  When no load
        !           101:  files are named, `gnuplot` enters into an interactive mode.  The special
        !           102:  filename "-" is used to denote standard input.  See "help batch/interactive"
        !           103:  for more details.
        !           104:
        !           105:  Many `gnuplot` commands have multiple options.  These options must appear in
        !           106:  the proper order, although unwanted ones may be omitted in most cases.  Thus
        !           107:  if the entire command is "command a b c", then "command a c" will probably
        !           108:  work, but "command c a" will fail.
        !           109:
        !           110:  Commands may extend over several input lines by ending each line but the last
        !           111:  with a backslash (\).  The backslash must be the _last_ character on each
        !           112:  line.  The effect is as if the backslash and newline were not there.  That
        !           113:  is, no white space is implied, nor is a comment terminated.  Therefore,
        !           114:  commenting out a continued line comments out the entire command (see
        !           115:  `comment`).  But note that if an error occurs somewhere on a multi-line
        !           116:  command, the parser may not be able to locate precisely where the error is
        !           117:  and in that case will not necessarily point to the correct line.
        !           118:
        !           119:  In this document, curly braces ({}) denote optional arguments and a vertical
        !           120:  bar (|) separates mutually exclusive choices.  `gnuplot` keywords or `help`
        !           121:  topics are indicated by backquotes or `boldface` (where available).  Angle
        !           122:  brackets (<>) are used to mark replaceable tokens.  In many cases, a default
        !           123:  value of the token will be taken for optional arguments if the token is
        !           124:  omitted, but these cases are not always denoted with braces around the angle
        !           125:  brackets.
        !           126:
        !           127:  For on-line help on any topic, type `help` followed by the name of the topic
        !           128:  or just `help` or `?` to get a menu of available topics.
        !           129:
        !           130:  The new `gnuplot` user should begin by reading about `plotting` (if on-line,
        !           131:  type `help plotting`).
        !           132: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/simple/simple.html"> Simple Plots Demo </a>
        !           133: 2 Seeking-assistance
        !           134: ?seeking-assistance
        !           135:  There is a mailing list for `gnuplot` users.  Note, however, that the
        !           136:  newsgroup
        !           137:        comp.graphics.apps.gnuplot
        !           138:  is identical to the mailing list (they both carry the same set of messages).
        !           139:  We prefer that you read the messages through the newsgroup rather than
        !           140:  subscribing to the mailing list.  Administrative requests should be sent to
        !           141:        majordomo@dartmouth.edu
        !           142:  Send a message with the body (not the subject) consisting of the single word
        !           143:  "help" (without the quotes) for more details.
        !           144:
        !           145:  The address for mailing to list members is:
        !           146:        info-gnuplot@dartmouth.edu
        !           147:
        !           148:  Bug reports and code contributions should be mailed to:
        !           149:        bug-gnuplot@dartmouth.edu
        !           150:
        !           151:  The list of those interested in beta-test versions is:
        !           152:        info-gnuplot-beta@dartmouth.edu
        !           153:
        !           154:  There is also a World Wide Web page with up-to-date information, including
        !           155:  known bugs:
        !           156: ^ <a href="http://www.cs.dartmouth.edu/gnuplot_info.html">
        !           157:        http://www.cs.dartmouth.edu/gnuplot_info.html
        !           158: ^ </a>
        !           159:
        !           160:  Before seeking help, please check the
        !           161: ^ <a href="http://www.uni-karlsruhe.de/~ig25/gnuplot-faq.html">
        !           162:  FAQ (Frequently Asked Questions) list.
        !           163: ^ </a>
        !           164:  If you do not have a copy of the FAQ, you may request a copy by email from
        !           165:  the Majordomo address above, ftp a copy from
        !           166:        ftp://ftp.dartmouth.edu/pub/gnuplot
        !           167:  or see the WWW `gnuplot` page.
        !           168:
        !           169:  When posting a question, please include full details of the version of
        !           170:  `gnuplot`, the machine, and operating system you are using.  A _small_ script
        !           171:  demonstrating the problem may be useful.  Function plots are preferable to
        !           172:  datafile plots.  If email-ing to info-gnuplot, please state whether or not
        !           173:  you are subscribed to the list, so that users who use news will know to email
        !           174:  a reply to you.  There is a form for such postings on the WWW site.
        !           175: 2 What's New in version 3.7
        !           176: ?new-features
        !           177:  Gnuplot version 3.7 contains many new features.  This section gives a partial
        !           178:  list and links to the new items in no particular order.
        !           179:
        !           180:  1. `fit f(x) 'file' via` uses the Marquardt-Levenberg method to fit data.
        !           181:  (This is only slightly different from the `gnufit` patch available for 3.5.)
        !           182:
        !           183:  2. Greatly expanded `using` command.  See `plot using`.
        !           184:
        !           185:  3. `set timefmt` allows for the use of dates as input and output for time
        !           186:  series plots.  See `Time/Date data` and
        !           187: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/timefmt/timefmt.html">
        !           188:  timedat.dem.
        !           189: ^ </a>
        !           190:
        !           191:  4. Multiline labels and font selection in some drivers.
        !           192:
        !           193:  5. Minor (unlabeled) tics.  See `set mxtics`.
        !           194:
        !           195:  6. `key` options for moving the key box in the page (and even outside of the
        !           196:  plot), putting a title on it and a box around it, and more.  See `set key`.
        !           197:
        !           198:  7. Multiplots on a single logical page with `set multiplot`.
        !           199:
        !           200:  8. Enhanced `postscript` driver with super/subscripts and font changes.
        !           201:  (This was a separate driver (`enhpost`) that was available as a patch for
        !           202:  3.5.)
        !           203:
        !           204:  9. Second axes:  use the top and right axes independently of the bottom and
        !           205:  left, both for plotting and labels.  See `plot`.
        !           206:
        !           207:  10. Special datafile names `'-'` and `""`.  See `plot special-filenames`.
        !           208:
        !           209:  11. Additional coordinate systems for labels and arrows.  See `coordinates`.
        !           210:
        !           211:  12. `set size` can try to plot with a specified aspect ratio.
        !           212:
        !           213:  13. `set missing` now treats missing data correctly.
        !           214:
        !           215:  14. The `call` command: `load` with arguments.
        !           216:
        !           217:  15. More flexible `range` commands with `reverse` and `writeback` keywords.
        !           218:
        !           219:  16. `set encoding` for multi-lingual encoding.
        !           220:
        !           221:  17. New `x11` driver with persistent and multiple windows.
        !           222:
        !           223:  18. New plotting styles: `xerrorbars`, `histeps`, `financebars` and more.
        !           224:  See `set style`.
        !           225:
        !           226:  19. New tic label formats, including `"%l %L"` which uses the mantissa and
        !           227:  exponents to a given base for labels.  See `set format`.
        !           228:
        !           229:  20. New drivers, including `cgm` for inclusion into MS-Office applications
        !           230:  and `gif` for serving plots to the WEB.
        !           231:
        !           232:  21. Smoothing and spline-fitting options for `plot`.  See `plot smooth`.
        !           233:
        !           234:  22. `set margin` and `set origin` give much better control over where a
        !           235:  graph appears on the page.
        !           236:
        !           237:  23. `set border` now controls each border individually.
        !           238:
        !           239:  24. The new commands `if` and `reread` allow command loops.
        !           240:
        !           241:  25. Point styles and sizes, line types and widths can be specified on the
        !           242:  `plot` command.  Line types and widths can also be specified for grids,
        !           243:  borders, tics and arrows.  See `plot with`.  Furthermore these types may be
        !           244:  combined and stored for further use.  See `set linestyle`.
        !           245:
        !           246:  26. Text (labels, tic labels, and the time stamp) can be written vertically
        !           247:  by those terminals capable of doing so.
        !           248: 2 Batch/Interactive Operation
        !           249: ?batch/interactive
        !           250:  `gnuplot` may be executed in either batch or interactive modes, and the two
        !           251:  may even be mixed together on many systems.
        !           252:
        !           253:  Any command-line arguments are assumed to be names of files containing
        !           254:  `gnuplot` commands (with the exception of standard X11 arguments, which are
        !           255:  processed first).  Each file is loaded with the `load` command, in the order
        !           256:  specified.  `gnuplot` exits after the last file is processed.  When no load
        !           257:  files are named, `gnuplot` enters into an interactive mode.  The special
        !           258:  filename "-" is used to denote standard input.
        !           259:
        !           260:  Both the `exit` and `quit` commands terminate the current command file and
        !           261:  `load` the next one, until all have been processed.
        !           262:
        !           263:  Examples:
        !           264:
        !           265:  To launch an interactive session:
        !           266:        gnuplot
        !           267:
        !           268:  To launch a batch session using two command files "input1" and "input2":
        !           269:        gnuplot input1 input2
        !           270:
        !           271:  To launch an interactive session after an initialization file "header" and
        !           272:  followed by another command file "trailer":
        !           273:        gnuplot header - trailer
        !           274: 2 Command-line-editing
        !           275: ?line-editing
        !           276: ?editing
        !           277: ?history
        !           278: ?command-line-editing
        !           279:  Command-line editing is supported by the Unix, Atari, VMS, MS-DOS and OS/2
        !           280:  versions of `gnuplot`.  Also, a history mechanism allows previous commands to
        !           281:  be edited and re-executed.  After the command line has been edited, a newline
        !           282:  or carriage return will enter the entire line without regard to where the
        !           283:  cursor is positioned.
        !           284:
        !           285:  (The readline function in `gnuplot` is not the same as the readline used in
        !           286:  GNU Bash and GNU Emacs.  If the GNU version is desired, it may be selected
        !           287:  instead of the `gnuplot` version at compile time.)
        !           288:
        !           289:
        !           290:  The editing commands are as follows:
        !           291:
        !           292: @start table - first is interactive cleartext form
        !           293:        `Line-editing`:
        !           294:
        !           295:        ^B    moves back a single character.
        !           296:        ^F    moves forward a single character.
        !           297:        ^A    moves to the beginning of the line.
        !           298:        ^E    moves to the end of the line.
        !           299:        ^H    and DEL delete the previous character.
        !           300:        ^D    deletes the current character.
        !           301:        ^K    deletes from current position to the end of line.
        !           302:        ^L,^R redraws line in case it gets trashed.
        !           303:        ^U    deletes the entire line.
        !           304:        ^W    deletes the last word.
        !           305:
        !           306:        `History`:
        !           307:
        !           308:        ^P    moves back through history.
        !           309:        ^N    moves forward through history.
        !           310: #\begin{tabular}{|cl|} \hline
        !           311: #\multicolumn{2}{|c|}{Command-line Editing Commands} \\ \hline \hline
        !           312: #Character & Function \\ \hline
        !           313: # & \multicolumn{1}{|c|}{Line Editing}\\ \cline{2-2}
        !           314: #\verb~^B~ & move back a single character.\\
        !           315: #\verb~^F~ & move forward a single character.\\
        !           316: #\verb~^A~ & move to the beginning of the line.\\
        !           317: #\verb~^E~ & move to the end of the line.\\
        !           318: #\verb~^H, DEL~ & delete the previous character.\\
        !           319: #\verb~^D~ & delete the current character.\\
        !           320: #\verb~^K~ & delete from current position to the end of line.\\
        !           321: #\verb~^L, ^R~ & redraw line in case it gets trashed.\\
        !           322: #\verb~^U~ & delete the entire line. \\
        !           323: #\verb~^W~ & delete from the current word to the end of line. \\ \hline
        !           324: # & \multicolumn{1}{|c|}{History} \\ \cline{2-2}
        !           325: #\verb~^P~ & move back through history.\\
        !           326: #\verb~^N~ & move forward through history.\\
        !           327: %c l .
        !           328: %Character@Function
        !           329: %_
        !           330: %@Line Editing
        !           331: %^B@move back a single character.
        !           332: %^F@move forward a single character.
        !           333: %^A@move to the beginning of the line.
        !           334: %^E@move to the end of the line.
        !           335: %^H, DEL@delete the previous character.
        !           336: %^D@delete the current character.
        !           337: %^K@delete from current position to the end of line.
        !           338: %^L, ^R@redraw line in case it gets trashed.
        !           339: %^U@delete the entire line.
        !           340: %^W@delete from the current word to the end of line.
        !           341: %_
        !           342: %@History
        !           343: %^P@move back through history.
        !           344: %^N@move forward through history.
        !           345: @end table
        !           346:
        !           347:  On the IBM PC, the use of a TSR program such as DOSEDIT or CED may be desired
        !           348:  for line editing.  The default makefile assumes that this is the case;  by
        !           349:  default `gnuplot` will be compiled with no line-editing capability.  If you
        !           350:  want to use `gnuplot`'s line editing, set READLINE in the makefile and add
        !           351:  readline.obj to the link file.  The following arrow keys may be used on the
        !           352:  IBM PC and Atari versions if readline is used:
        !           353:
        !           354: @start table - first is interactive cleartext form
        !           355:        Left  Arrow      - same as ^B.
        !           356:        Right Arrow      - same as ^F.
        !           357:        Ctrl Left  Arrow - same as ^A.
        !           358:        Ctrl Right Arrow - same as ^E.
        !           359:        Up    Arrow      - same as ^P.
        !           360:        Down  Arrow      - same as ^N.
        !           361: #\begin{tabular}{|cl|} \hline
        !           362: #Arrow key  & Function \\ \hline
        !           363: #Left       & same as \verb~^B~. \\
        !           364: #Right      & same as \verb~^F~. \\
        !           365: #Ctrl Left  & same as \verb~^A~. \\
        !           366: #Ctrl Right & same as \verb~^E~. \\
        !           367: #Up         & same as \verb~^P~. \\
        !           368: #Down       & same as \verb~^N~. \\
        !           369: %c l .
        !           370: %Arrow key@Function
        !           371: %_
        !           372: %Left Arrow@same as ^B.
        !           373: %Right Arrow@same as ^F.
        !           374: %Ctrl Left Arrow@same as ^A.
        !           375: %Ctrl Right Arrow@same as ^E.
        !           376: %Up Arrow@same as ^P.
        !           377: %Down Arrow@same as ^N.
        !           378: %_
        !           379: @end table
        !           380:
        !           381:  The Atari version of readline defines some additional key aliases:
        !           382:
        !           383: @start table - first is interactive cleartext form
        !           384:        Undo            - same as ^L.
        !           385:        Home            - same as ^A.
        !           386:        Ctrl Home       - same as ^E.
        !           387:        Esc             - same as ^U.
        !           388:        Help            - `help` plus return.
        !           389:        Ctrl Help       - `help `.
        !           390: #\begin{tabular}{|cl|} \hline
        !           391: #Arrow key & Function \\ \hline
        !           392: #Undo      & same as \verb~^L~. \\
        !           393: #Home      & same as \verb~^A~. \\
        !           394: #Ctrl Home & same as \verb~^E~. \\
        !           395: #Esc       & same as \verb~^U~. \\
        !           396: #Help      & `{\bf help}' plus return. \\
        !           397: #Ctrl Help & `{\bf help }'. \\
        !           398: %c l .
        !           399: %Arrow key@Function
        !           400: %_
        !           401: %Undo@same as ^L.
        !           402: %Home@same as ^A.
        !           403: %Ctrl Home@same as ^E.
        !           404: %Esc@same as ^U.
        !           405: %Help@help plus return.
        !           406: %Ctrl Help@help .
        !           407: %_
        !           408: @end table
        !           409: 2 Comments
        !           410: ?comments
        !           411:  Comments are supported as follows: a `#` may appear in most places in a line
        !           412:  and `gnuplot` will ignore the rest of the line.  It will not have this effect
        !           413:  inside quotes, inside numbers (including complex numbers), inside command
        !           414:  substitutions, etc.  In short, it works anywhere it makes sense to work.
        !           415: 2 Coordinates
        !           416: ?coordinates
        !           417:  The commands `set arrow`, `set key`, and `set label` allow you to draw
        !           418:  something at an arbitrary position on the graph.  This position is specified
        !           419:  by the syntax:
        !           420:
        !           421:        {<system>} <x>, {<system>} <y> {,{<system>} <z>}
        !           422:
        !           423:  Each <system> can either be `first`, `second`, `graph` or `screen`.
        !           424:
        !           425:  `first` places the x, y, or z coordinate in the system defined by the left
        !           426:  and bottom axes; `second` places it in the system defined by the second axes
        !           427:  (top and right); `graph` specifies the area within the axes---0,0 is bottom
        !           428:  left and 1,1 is top right (for splot, 0,0,0 is bottom left of plotting area;
        !           429:  use negative z to get to the base---see `set ticslevel`); and `screen`
        !           430:  specifies the screen area (the entire area---not just the portion selected by
        !           431:  `set size`), with 0,0 at bottom left and 1,1 at top right.
        !           432:
        !           433:  If the coordinate system for x is not specified, `first` is used.  If the
        !           434:  system for y is not specified, the one used for x is adopted.
        !           435:
        !           436:  If one (or more) axis is timeseries, the appropriate coordinate should
        !           437:  be given as a quoted time string according to the `timefmt` format string.
        !           438:  See `set xdata` and `set timefmt`.  `gnuplot` will also accept an integer
        !           439:  expression, which will be interpreted as seconds from 1 January 2000.
        !           440: 2 Environment
        !           441: ?environment
        !           442:  A number of shell environment variables are understood by `gnuplot`.  None of
        !           443:  these are required, but may be useful.
        !           444:
        !           445:  If GNUTERM is defined, it is used as the name of the terminal type to be
        !           446:  used.  This overrides any terminal type sensed by `gnuplot` on start-up, but
        !           447:  is itself overridden by the .gnuplot (or equivalent) start-up file (see
        !           448:  `start-up`) and, of course, by later explicit changes.
        !           449:
        !           450:  On Unix, AmigaOS, AtariTOS, MS-DOS and OS/2, GNUHELP may be defined to be the
        !           451:  pathname of the HELP file (gnuplot.gih).
        !           452:
        !           453:  On VMS, the logical name GNUPLOT$HELP should be defined as the name of the
        !           454:  help library for `gnuplot`.  The `gnuplot` help can be put inside any system
        !           455:  help library, allowing access to help from both within and outside `gnuplot`
        !           456:  if desired.
        !           457:
        !           458:  On Unix, HOME is used as the name of a directory to search for a .gnuplot
        !           459:  file if none is found in the current directory.  On AmigaOS, AtariTOS,
        !           460:  MS-DOS and OS/2, gnuplot is used.  On VMS, SYS$LOGIN: is used. See `help
        !           461:  start-up`.
        !           462:
        !           463:  On Unix, PAGER is used as an output filter for help messages.
        !           464:
        !           465:  On Unix, AtariTOS and AmigaOS, SHELL is used for the `shell` command.  On
        !           466:  MS-DOS and OS/2, COMSPEC is used for the `shell` command.
        !           467:
        !           468:  On MS-DOS, if the BGI or Watcom interface is used, PCTRM is used to tell
        !           469:  the maximum resolution supported by your monitor by setting it to
        !           470:  S<max. horizontal resolution>. E.g. if your monitor's maximum resolution is
        !           471:  800x600, then use:
        !           472:        set PCTRM=S800
        !           473:  If PCTRM is not set, standard VGA is used.
        !           474:
        !           475:  FIT_SCRIPT may be used to specify a `gnuplot` command to be executed when a
        !           476:  fit is interrupted---see `fit`.  FIT_LOG specifies the filename of the
        !           477:  logfile maintained by fit.
        !           478: 2 Expressions
        !           479: ?expressions
        !           480:  In general, any mathematical expression accepted by C, FORTRAN, Pascal, or
        !           481:  BASIC is valid.  The precedence of these operators is determined by the
        !           482:  specifications of the C programming language.  White space (spaces and tabs)
        !           483:  is ignored inside expressions.
        !           484:
        !           485:  Complex constants are expressed as {<real>,<imag>}, where <real> and <imag>
        !           486:  must be numerical constants.  For example, {3,2} represents 3 + 2i; {0,1}
        !           487:  represents 'i' itself.  The curly braces are explicitly required here.
        !           488:
        !           489:  Note that gnuplot uses both "real" and "integer" arithmetic, like FORTRAN and
        !           490:  C.  Integers are entered as "1", "-10", etc; reals as "1.0", "-10.0", "1e1",
        !           491:  3.5e-1, etc.  The most important difference between the two forms is in
        !           492:  division: division of integers truncates: 5/2 = 2; division of reals does
        !           493:  not: 5.0/2.0 = 2.5.  In mixed expressions, integers are "promoted" to reals
        !           494:  before evaluation: 5/2e0 = 2.5.  The result of division of a negative integer
        !           495:  by a positive one may vary among compilers.  Try a test like "print -5/2" to
        !           496:  determine if your system chooses -2 or -3 as the answer.
        !           497:
        !           498:  The integer expression "1/0" may be used to generate an "undefined" flag,
        !           499:  which causes a point to ignored; the `ternary` operator gives an example.
        !           500:
        !           501:  The real and imaginary parts of complex expressions are always real, whatever
        !           502:  the form in which they are entered: in {3,2} the "3" and "2" are reals, not
        !           503:  integers.
        !           504: 3 Functions
        !           505: ?expressions functions
        !           506: ?functions
        !           507:  The functions in `gnuplot` are the same as the corresponding functions in
        !           508:  the Unix math library, except that all functions accept integer, real, and
        !           509:  complex arguments, unless otherwise noted.
        !           510:
        !           511:  For those functions that accept or return angles that may be given in either
        !           512:  degrees or radians (sin(x), cos(x), tan(x), asin(x), acos(x), atan(x),
        !           513:  atan2(x) and arg(z)), the unit may be selected by `set angles`, which
        !           514:  defaults to radians.
        !           515:
        !           516: @start table
        !           517: #\begin{tabular}{|ccl|} \hline
        !           518: #\multicolumn{3}{|c|}{Math library functions} \\ \hline \hline
        !           519: #Function & Arguments & Returns \\ \hline
        !           520: %c c l .
        !           521: %Function@Arguments@Returns
        !           522: %_
        !           523: 4 abs
        !           524: ?expressions functions abs
        !           525: ?functions abs
        !           526: ?abs
        !           527: #abs(x) & any  &  absolute value of $x$, $|x|$; same type \\
        !           528: #abs(x) & complex &  length of $x$, $\sqrt{{\mbox{real}(x)^{2} +
        !           529: #\mbox{imag}(x)^{2}}}$ \\
        !           530: %abs(x)@any@absolute value of $x$, $|x|$; same type
        !           531: %abs(x)@complex@length of $x$, $sqrt{roman real (x) sup 2 + roman imag (x) sup 2}$
        !           532:  The `abs` function returns the absolute value of its argument.  The returned
        !           533:  value is of the same type as the argument.
        !           534:
        !           535:  For complex arguments, abs(x) is defined as the length of x in the complex
        !           536:  plane [i.e.,  sqrt(real(x)**2 + imag(x)**2) ].
        !           537: 4 acos
        !           538: ?expressions functions acos
        !           539: ?functions acos
        !           540: ?acos
        !           541: #acos(x) & any  & $\cos^{-1} x$ (inverse cosine) \\
        !           542: %acos(x)@any@$cos sup -1 x$ (inverse cosine)
        !           543:  The `acos` function returns the arc cosine (inverse cosine) of its argument.
        !           544:  `acos` returns its argument in radians or degrees, as selected by `set
        !           545:  angles`.
        !           546: 4 acosh
        !           547: ?expressions functions acosh
        !           548: ?functions acosh
        !           549: ?acosh
        !           550: #acosh(x) & any  & $\cosh^{-1} x$ (inverse hyperbolic cosine) in radians \\
        !           551: %acosh(x)@any@$cosh sup -1 x$ (inverse hyperbolic cosine) in radians
        !           552:  The `acosh` function returns the inverse hyperbolic cosine of its argument in
        !           553:  radians.
        !           554: 4 arg
        !           555: ?expressions functions arg
        !           556: ?functions arg
        !           557: ?arg
        !           558: #arg(x) & complex & the phase of $x$ \\
        !           559: %arg(x)@complex@the phase of $x$
        !           560:  The `arg` function returns the phase of a complex number in radians or
        !           561:  degrees, as selected by `set angles`.
        !           562: 4 asin
        !           563: ?expressions functions asin
        !           564: ?functions asin
        !           565: ?asin
        !           566: #asin(x) & any  & $\sin^{-1} x$ (inverse sin) \\
        !           567: %asin(x)@any@$sin sup -1 x$ (inverse sin)
        !           568:  The `asin` function returns the arc sin (inverse sin) of its argument.
        !           569:  `asin` returns its argument in radians or degrees, as selected by `set
        !           570:  angles`.
        !           571: 4 asinh
        !           572: ?expressions functions asinh
        !           573: ?functions asinh
        !           574: ?asinh
        !           575: #asinh(x) & any  & $\sinh^{-1} x$ (inverse hyperbolic sin) in radians \\
        !           576: %asinh(x)@any@$sinh sup -1 x$ (inverse hyperbolic sin) in radians
        !           577:  The `asinh` function returns the inverse hyperbolic sin of its argument in
        !           578:  radians.
        !           579: 4 atan
        !           580: ?expressions functions atan
        !           581: ?functions atan
        !           582: ?atan
        !           583: #atan(x) & any  & $\tan^{-1} x$ (inverse tangent) \\
        !           584: %atan(x)@any@$tan sup -1 x$ (inverse tangent)
        !           585:  The `atan` function returns the arc tangent (inverse tangent) of its
        !           586:  argument.  `atan` returns its argument in radians or degrees, as selected by
        !           587:  `set angles`.
        !           588: 4 atan2
        !           589: ?expressions functions atan2
        !           590: ?functions atan2
        !           591: ?atan2
        !           592: #atan2(y,x) & int or real & $\tan^{-1} (y/x)$ (inverse tangent) \\
        !           593: %atan2(y,x)@int or real@$tan sup -1 (y/x)$ (inverse tangent)
        !           594:  The `atan2` function returns the arc tangent (inverse tangent) of the ratio
        !           595:  of the real parts of its arguments.  `atan2` returns its argument in radians
        !           596:  or degrees, as selected by `set angles`, in the correct quadrant.
        !           597: 4 atanh
        !           598: ?expressions functions atanh
        !           599: ?functions atanh
        !           600: ?atan
        !           601: #atanh(x) & any  & $\tanh^{-1} x$ (inverse hyperbolic tangent) in radians \\
        !           602: %atanh(x)@any@$tanh sup -1 x$ (inverse hyperbolic tangent) in radians
        !           603:  The `atanh` function returns the inverse hyperbolic tangent of its argument
        !           604:  in radians.
        !           605: 4 besj0
        !           606: ?expressions functions besj0
        !           607: ?functions besj0
        !           608: ?besj0
        !           609: #besj0(x) & int or real &  $j_{0}$ Bessel function of $x$, in radians \\
        !           610: %besj0(x)@int or real@$j sub 0$ Bessel function of $x$, in radians
        !           611:  The `besj0` function returns the j0th Bessel function of its argument.
        !           612:  `besj0` expects its argument to be in radians.
        !           613: 4 besj1
        !           614: ?expressions functions besj1
        !           615: ?functions besj1
        !           616: ?besj1
        !           617: #besj1(x) & int or real & $j_{1}$ Bessel function of $x$, in radians \\
        !           618: %besj1(x)@int or real@$j sub 1$ Bessel function of $x$, in radians
        !           619:  The `besj1` function returns the j1st Bessel function of its argument.
        !           620:  `besj1` expects its argument to be in radians.
        !           621: 4 besy0
        !           622: ?expressions functions besy0
        !           623: ?functions besy0
        !           624: ?besy0
        !           625: #besy0(x) & int or real & $y_{0}$ Bessel function of $x$, in radians \\
        !           626: %besy0(x)@int or real@$y sub 0$ Bessel function of $x$, in radians
        !           627:  The `besy0` function returns the y0th Bessel function of its argument.
        !           628:  `besy0` expects its argument to be in radians.
        !           629: 4 besy1
        !           630: ?expressions functions besy1
        !           631: ?functions besy1
        !           632: ?besy1
        !           633: #besy1(x) & int or real & $y_{1}$ Bessel function of $x$, in radians \\
        !           634: %besy1(x)@int or real@$y sub 1$ Bessel function of $x$, in radians
        !           635:  The `besy1` function returns the y1st Bessel function of its argument.
        !           636:  `besy1` expects its argument to be in radians.
        !           637: 4 ceil
        !           638: ?expressions functions ceil
        !           639: ?functions ceil
        !           640: ?ceil
        !           641: #ceil(x) & any & $\lceil x \rceil$, smallest integer not less than $x$
        !           642: #(real part) \\
        !           643: %ceil(x)@any@$left ceiling x right ceiling$, smallest integer not less than $x$ (real part)
        !           644:  The `ceil` function returns the smallest integer that is not less than its
        !           645:  argument.  For complex numbers, `ceil` returns the smallest integer not less
        !           646:  than the real part of its argument.
        !           647: 4 cos
        !           648: ?expressions functions cos
        !           649: ?functions cos
        !           650: ?cos
        !           651: #cos(x) & any & $\cos x$, cosine of $x$ \\
        !           652: %cos(x)@radians@$cos~x$, cosine of $x$
        !           653:  The `cos` function returns the cosine of its argument.  `cos` accepts its
        !           654:  argument in radians or degrees, as selected by `set angles`.
        !           655: 4 cosh
        !           656: ?expressions functions cosh
        !           657: ?functions cosh
        !           658: ?cosh
        !           659: #cosh(x) & any & $\cosh x$, hyperbolic cosine of $x$ in radians \\
        !           660: %cosh(x)@any@$cosh~x$, hyperbolic cosine of $x$ in radians
        !           661:  The `cosh` function returns the hyperbolic cosine of its argument.  `cosh`
        !           662:  expects its argument to be in radians.
        !           663: 4 erf
        !           664: ?expressions functions erf
        !           665: ?functions erf
        !           666: ?erf
        !           667: #erf(x) & any & $\mbox{erf}(\mbox{real}(x))$,  error function of real($x$) \\
        !           668: %erf(x)@any@$erf ( roman real (x))$, error function of real ($x$)
        !           669:  The `erf` function returns the error function of the real part of its
        !           670:  argument.  If the argument is a complex value, the imaginary component is
        !           671:  ignored.
        !           672: 4 erfc
        !           673: ?expressions functions erfc
        !           674: ?functions erfc
        !           675: ?erfc
        !           676: #erfc(x) & any & $\mbox{erfc}(\mbox{real}(x))$,  1.0 - error function of real($x$) \\
        !           677: %erfc(x)@any@$erfc ( roman real (x))$, 1.0 - error function of real ($x$)
        !           678:  The `erfc` function returns 1.0 - the error function of the real part of its
        !           679:  argument.  If the argument is a complex value, the imaginary component is
        !           680:  ignored.
        !           681: 4 exp
        !           682: ?expressions functions exp
        !           683: ?functions exp
        !           684: ?exp
        !           685: #exp(x) & any & $e^{x}$,  exponential function of $x$ \\
        !           686: %exp(x)@any@$e sup x$, exponential function of $x$
        !           687:  The `exp` function returns the exponential function of its argument (`e`
        !           688:  raised to the power of its argument).  On some implementations (notably
        !           689:  suns), exp(-x) returns undefined for very large x.  A user-defined function
        !           690:  like safe(x) = x<-100 ? 0 : exp(x) might prove useful in these cases.
        !           691: 4 floor
        !           692: ?expressions functions floor
        !           693: ?functions floor
        !           694: ?floor
        !           695: #floor(x) & any & $\lfloor x \rfloor$,  largest integer not greater
        !           696: #than $x$ (real part) \\
        !           697: %floor(x)@any@$left floor x right floor$, largest integer not greater than $x$ (real part)
        !           698:  The `floor` function returns the largest integer not greater than its
        !           699:  argument.  For complex numbers, `floor` returns the largest integer not
        !           700:  greater than the real part of its argument.
        !           701: 4 gamma
        !           702: ?expressions functions gamma
        !           703: ?functions gamma
        !           704: ?gamma
        !           705: #gamma(x) & any & $\mbox{gamma}(\mbox{real}(x))$,  gamma function of real($x$) \\
        !           706: %gamma(x)@any@$GAMMA ( roman real (x))$, gamma function of real ($x$)
        !           707:  The `gamma` function returns the gamma function of the real part of its
        !           708:  argument.  For integer n, gamma(n+1) = n!.  If the argument is a complex
        !           709:  value, the imaginary component is ignored.
        !           710: 4 ibeta
        !           711: ?expressions functions ibeta
        !           712: ?functions ibeta
        !           713: ?ibeta
        !           714: #ibeta(p,q,x) & any & $\mbox{ibeta}(\mbox{real}(p,q,x))$,  ibeta function of real($p$,$q$,$x$) \\
        !           715: %ibeta(p,q,x)@any@$ibeta ( roman real (p,q,x))$, ibeta function of real ($p$,$q$,$x$)
        !           716:  The `ibeta` function returns the incomplete beta function of the real parts
        !           717:  of its arguments. p, q > 0 and x in [0:1].  If the arguments are complex,
        !           718:  the imaginary components are ignored.
        !           719: 4 inverf
        !           720: ?expressions functions inverf
        !           721: ?functions inverf
        !           722: ?inverf
        !           723: #inverf(x) & any &  inverse error function of real($x$)  \\
        !           724: %inverf(x)@any@inverse error function real($x$)
        !           725:  The `inverf` function returns the inverse error function of the real part
        !           726:  of its argument.
        !           727: 4 igamma
        !           728: ?expressions functions igamma
        !           729: ?functions igamma
        !           730: ?igamma
        !           731: #igamma(a,x) & any & $\mbox{igamma}(\mbox{real}(a,x))$,  igamma function of real($a$,$x$) \\
        !           732: %igamma(a,x)@any@$igamma ( roman real (a,x))$, igamma function of real ($a$,$x$)
        !           733:  The `igamma` function returns the incomplete gamma function of the real
        !           734:  parts of its arguments.  a > 0 and x >= 0.  If the arguments are complex,
        !           735:  the imaginary components are ignored.
        !           736: 4 imag
        !           737: ?expressions functions imag
        !           738: ?functions imag
        !           739: ?imag
        !           740: #imag(x) & complex &  imaginary part of $x$ as a real number \\
        !           741: %imag(x)@complex@imaginary part of $x$ as a real number
        !           742:  The `imag` function returns the imaginary part of its argument as a real
        !           743:  number.
        !           744: 4 invnorm
        !           745: ?expressions functions invnorm
        !           746: ?functions invnorm
        !           747: ?invnorm
        !           748: #invnorm(x) & any &  inverse normal distribution function of real($x$)  \\
        !           749: %invnorm(x)@any@inverse normal distribution function real($x$)
        !           750:  The `invnorm` function returns the inverse normal distribution function of
        !           751:  the real part of its argument.
        !           752: 4 int
        !           753: ?expressions functions int
        !           754: ?functions int
        !           755: ?int
        !           756: #int(x) & real &  integer part of $x$, truncated toward zero \\
        !           757: %int(x)@real@integer part of $x$, truncated toward zero
        !           758:  The `int` function returns the integer part of its argument, truncated
        !           759:  toward zero.
        !           760: 4 lgamma
        !           761: ?expressions functions lgamma
        !           762: ?functions lgamma
        !           763: ?lgamma
        !           764: #lgamma(x) & any & $\mbox{lgamma}(\mbox{real}(x))$,  lgamma function of real($x$) \\
        !           765: %lgamma(x)@any@$lgamma ( roman real (x))$, lgamma function of real ($x$)
        !           766:  The `lgamma` function returns the natural logarithm of the gamma function
        !           767:  of the real part of its argument.  If the argument is a complex value, the
        !           768:  imaginary component is ignored.
        !           769: 4 log
        !           770: ?expressions functions log
        !           771: ?functions log
        !           772: ?log
        !           773: #log(x) & any & $\log_{e} x$,  natural logarithm (base $e$) of $x$ \\
        !           774: %log(x)@any@$ln~x$, natural logarithm (base $e$) of $x$
        !           775:  The `log` function returns the natural logarithm (base `e`) of its argument.
        !           776: 4 log10
        !           777: ?expressions functions log10
        !           778: ?functions log10
        !           779: ?log10
        !           780: #log10(x) & any & $\log_{10} x$,  logarithm (base $10$) of $x$ \\
        !           781: %log10(x)@any@${log sub 10}~x$, logarithm (base $10$) of $x$
        !           782:  The `log10` function returns the logarithm (base 10) of its argument.
        !           783: 4 norm
        !           784: ?expressions functions norm
        !           785: ?functions norm
        !           786: ?norm
        !           787: #norm(x) & any & normal distribution (Gaussian) function of real($x$) \\
        !           788: %norm(x)@any@$norm(x)$, normal distribution function of real($x$)
        !           789:  The `norm` function returns the normal distribution function (or Gaussian)
        !           790:  of the real part of its argument.
        !           791: 4 rand
        !           792: ?expressions functions rand
        !           793: ?functions rand
        !           794: ?rand
        !           795: #rand(x) & any & $\mbox{rand}(\mbox{real}(x))$,  pseudo random number generator \\
        !           796: %rand(x)@any@$rand ( roman real (x))$, pseudo random number generator
        !           797:  The `rand` function returns a pseudo random number in the interval [0:1]
        !           798:  using the real part of its argument as a seed.  If seed < 0, the sequence
        !           799:  is (re)initialized.  If the argument is a complex value, the imaginary
        !           800:  component is ignored.
        !           801: 4 real
        !           802: ?expressions functions real
        !           803: ?functions real
        !           804: ?real
        !           805: #real(x) & any &  real part of $x$ \\
        !           806: %real(x)@any@real part of $x$
        !           807:  The `real` function returns the real part of its argument.
        !           808: 4 sgn
        !           809: ?expressions functions sgn
        !           810: ?functions sgn
        !           811: ?sgn
        !           812: #sgn(x) & any & 1 if $x>0$, -1 if $x<0$, 0 if $x=0$. imag($x$) ignored \\
        !           813: %sgn(x)@any@1 if $x > 0$, -1 if $x < 0$, 0 if $x = 0$. $roman imag (x)$ ignored
        !           814:  The `sgn` function returns 1 if its argument is positive, -1 if its argument
        !           815:  is negative, and 0 if its argument is 0.  If the argument is a complex value,
        !           816:  the imaginary component is ignored.
        !           817: 4 sin
        !           818: ?expressions functions sin
        !           819: ?functions sin
        !           820: ?sin
        !           821: #sin(x) & any & $\sin x$, sine of $x$ \\
        !           822: %sin(x)@any@$sin~x$, sine of $x$
        !           823:  The `sin` function returns the sine of its argument.  `sin` expects its
        !           824:  argument to be in radians or degrees, as selected by `set angles`.
        !           825: 4 sinh
        !           826: ?expressions functions sinh
        !           827: ?functions sinh
        !           828: ?sinh
        !           829: #sinh(x) & any & $\sinh x$, hyperbolic sine $x$ in radians \\
        !           830: %sinh(x)@any@$sinh~x$, hyperbolic sine $x$ in radians
        !           831:  The `sinh` function returns the hyperbolic sine of its argument.  `sinh`
        !           832:  expects its argument to be in radians.
        !           833: 4 sqrt
        !           834: ?expressions functions sqrt
        !           835: ?functions sqrt
        !           836: ?sqrt
        !           837: #sqrt(x) & any & $\sqrt{x}$,  square root of $x$ \\
        !           838: %sqrt(x)@any@$sqrt x $, square root of $x$
        !           839:  The `sqrt` function returns the square root of its argument.
        !           840: 4 tan
        !           841: ?expressions functions tan
        !           842: ?functions tan
        !           843: ?tan
        !           844: #tan(x) & any & $\tan x$,  tangent of $x$ \\
        !           845: %tan(x)@any@$tan~x$, tangent of $x$
        !           846:  The `tan` function returns the tangent of its argument.  `tan` expects
        !           847:  its argument to be in radians or degrees, as selected by `set angles`.
        !           848: 4 tanh
        !           849: ?expressions functions tanh
        !           850: ?functions tanh
        !           851: ?tanh
        !           852: #tanh(x) & any & $\tanh x$, hyperbolic tangent of $x$ in radians\\
        !           853: %tanh(x)@any@$tanh~x$, hyperbolic tangent of $x$ in radians
        !           854:  The `tanh` function returns the hyperbolic tangent of its argument.  `tanh`
        !           855:  expects its argument to be in radians.
        !           856: @end table
        !           857:
        !           858:  A few additional functions are also available.
        !           859:
        !           860: @start table
        !           861: #\begin{tabular}{|ccl|} \hline
        !           862: #\multicolumn{3}{|c|}{other {\bf gnuplot} functions} \\ \hline \hline
        !           863: #Function & Arguments & Returns \\ \hline
        !           864: %c c l .
        !           865: %Function@Arguments@Returns
        !           866: %_
        !           867: 4 column
        !           868: ?expressions functions column
        !           869: ?functions column
        !           870: ?column
        !           871: #column(x) & int & column $x$ during datafile manipulation. \\
        !           872: %column(x)@int@ column $x$ during datafile manipulation.
        !           873:  `column(x)` may be used only in expressions as part of `using` manipulations
        !           874:  to fits or datafile plots.  See `plot datafile using`.
        !           875: 4 tm_hour
        !           876: ?expressions tm_hour
        !           877: ?functions tm_hour
        !           878: #tm\_hour(x) & int & the hour \\
        !           879: %tm_hour(x)@int@the hour
        !           880:  The `tm_hour` function interprets its argument as a time, in seconds from
        !           881:  1 Jan 2000.  It returns the hour (an integer in the range 0--23) as a real.
        !           882: 4 tm_mday
        !           883: ?expressions tm_mday
        !           884: ?functions tm_mday
        !           885: #tm\_mday(x) & int & the day of the month \\
        !           886: %tm_mday(x)@int@the day of the month
        !           887:  The `tm_mday` function interprets its argument as a time, in seconds from
        !           888:  1 Jan 2000.  It returns the day of the month (an integer in the range 1--31)
        !           889:  as a real.
        !           890: 4 tm_min
        !           891: ?expressions tm_min
        !           892: ?functions tm_min
        !           893: #tm\_min(x) & int & the minute \\
        !           894: %tm_min(x)@int@the minute
        !           895:  The `tm_min` function interprets its argument as a time, in seconds from
        !           896:  1 Jan 2000.  It returns the minute (an integer in the range 0--59) as a real.
        !           897: 4 tm_mon
        !           898: ?expressions tm_mon
        !           899: ?functions tm_mon
        !           900: #tm\_mon(x) & int & the month \\
        !           901: %tm_mon(x)@int@the month
        !           902:  The `tm_mon` function interprets its argument as a time, in seconds from
        !           903:  1 Jan 2000.  It returns the month (an integer in the range 1--12) as a real.
        !           904: 4 tm_sec
        !           905: ?expressions tm_sec
        !           906: ?functions tm_sec
        !           907: #tm\_sec(x) & int & the second \\
        !           908: %tm_sec(x)@int@the second
        !           909:  The `tm_sec` function interprets its argument as a time, in seconds from
        !           910:  1 Jan 2000.  It returns the second (an integer in the range 0--59) as a real.
        !           911: 4 tm_wday
        !           912: ?expressions tm_wday
        !           913: ?functions tm_wday
        !           914: #tm\_wday(x) & int & the day of the week \\
        !           915: %tm_wday(x)@int@the day of the week
        !           916:  The `tm_wday` function interprets its argument as a time, in seconds from
        !           917:  1 Jan 2000.  It returns the day of the week (an integer in the range 1--7) as
        !           918:  a real.
        !           919: 4 tm_yday
        !           920: ?expressions tm_yday
        !           921: ?functions tm_yday
        !           922: #tm\_yday(x) & int & the day of the year \\
        !           923: %tm_yday(x)@int@the day of the year
        !           924:  The `tm_yday` function interprets its argument as a time, in seconds from
        !           925:  1 Jan 2000.  It returns the day of the year (an integer in the range 1--366)
        !           926:  as a real.
        !           927: 4 tm_year
        !           928: ?expressions tm_year
        !           929: ?functions tm_year
        !           930: #tm\_year(x) & int & the year \\
        !           931: %tm_year(x)@int@the year
        !           932:  The `tm_year` function interprets its argument as a time, in seconds from
        !           933:  1 Jan 2000.  It returns the year (an integer) as a real.
        !           934: 4 valid
        !           935: ?expressions functions valid
        !           936: ?functions valid
        !           937: ?valid
        !           938: #valid(x) & int & test validity of $\mbox{column}(x)$ during datafile manip.\\
        !           939: %valid(x)@int@ test validity of column($x$) during datafile manip.
        !           940:  `valid(x)` may be used only in expressions as part of `using` manipulations
        !           941:  to fits or datafile plots.  See `plot datafile using`.
        !           942: @end table
        !           943: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/airfoil/airfoil.html">Use of functions and complex variables for airfoils </a>
        !           944: 3 Operators
        !           945: ?expressions operators
        !           946: ?operators
        !           947:  The operators in `gnuplot` are the same as the corresponding operators in the
        !           948:  C programming language, except that all operators accept integer, real, and
        !           949:  complex arguments, unless otherwise noted.  The ** operator (exponentiation)
        !           950:  is supported, as in FORTRAN.
        !           951:
        !           952:  Parentheses may be used to change order of evaluation.
        !           953: 4 Unary
        !           954: ?expressions operators unary
        !           955: ?operators unary
        !           956: ?unary
        !           957:  The following is a list of all the unary operators and their usages:
        !           958:
        !           959: @start table - first is interactive cleartext form
        !           960:      Symbol      Example    Explanation
        !           961:        -           -a          unary minus
        !           962:        +           +a          unary plus (no-operation)
        !           963:        ~           ~a        * one's complement
        !           964:        !           !a        * logical negation
        !           965:        !           a!        * factorial
        !           966:        $           $3        * call arg/column during `using` manipulation
        !           967: #\begin{tabular}{|ccl|} \hline
        !           968: #\multicolumn{3}{|c|}{Unary Operators}\\ \hline \hline
        !           969: #Symbol & Example & Explanation \\ \hline
        !           970: #\verb@-@ & \verb@-a@ & unary minus \\
        !           971: #\verb@+@ & \verb@+a@ & unary plus (no-operation) \\
        !           972: #\verb@~@ & \verb@~a@ & * one's complement \\
        !           973: #\verb@!@ & \verb@!a@ & * logical negation \\
        !           974: #\verb@!@ & \verb@a!@ & * factorial \\
        !           975: #\verb@$@ & \verb@$3@ & * call arg/column during `using` manipulation \\
        !           976: C ugly hack: doc2ms uses $ as delimiter for eqn's so it doesn't seem to
        !           977: C be able to print them. So we have to typeset this table without using
        !           978: C eqn (at least that's the only solution I found, without any real docs
        !           979: C on *roff and eqn
        !           980: C First, terminate the table doc2ms.c already started:
        !           981: %.TE
        !           982: C ... then turn off eqn delimiters:
        !           983: %.EQ
        !           984: %delim off
        !           985: %.EN
        !           986: C ... and restart the table:
        !           987: %.TS
        !           988: %center box tab (@) ;
        !           989: %c c l .
        !           990: %Symbol@Example@Explanation
        !           991: %_
        !           992: %-@-a@unary minus
        !           993: %+@+a@unary plus (no-operation)
        !           994: %~@~a@* one's complement
        !           995: %!@!a@* logical negation
        !           996: %!@a!@* factorial
        !           997: %$@$3@* call arg/column during `using` manipulation
        !           998: %_
        !           999: @end table
        !          1000:  (*) Starred explanations indicate that the operator requires an integer
        !          1001:  argument.
        !          1002:
        !          1003:  Operator precedence is the same as in Fortran and C.  As in those languages,
        !          1004:  parentheses may be used to change the order of operation.  Thus -2**2 = -4,
        !          1005:  but (-2)**2 = 4.
        !          1006:
        !          1007:  The factorial operator returns a real number to allow a greater range.
        !          1008: 4 Binary
        !          1009: ?expressions operators binary
        !          1010: ?operators binary
        !          1011: ?binary
        !          1012:  The following is a list of all the binary operators and their usages:
        !          1013:
        !          1014: @start table - first is interactive cleartext form
        !          1015:      Symbol       Example      Explanation
        !          1016:        **          a**b          exponentiation
        !          1017:        *           a*b           multiplication
        !          1018:        /           a/b           division
        !          1019:        %           a%b         * modulo
        !          1020:        +           a+b           addition
        !          1021:        -           a-b           subtraction
        !          1022:        ==          a==b          equality
        !          1023:        !=          a!=b          inequality
        !          1024:        <           a<b           less than
        !          1025:        <=          a<=b          less than or equal to
        !          1026:        >           a>b           greater than
        !          1027:        >=          a>=b          greater than or equal to
        !          1028:        &           a&b         * bitwise AND
        !          1029:        ^           a^b         * bitwise exclusive OR
        !          1030:        |           a|b         * bitwise inclusive OR
        !          1031:        &&          a&&b        * logical AND
        !          1032:        ||          a||b        * logical OR
        !          1033: #\begin{tabular}{|ccl|} \hline
        !          1034: #\multicolumn{3}{|c|}{Binary Operators} \\ \hline \hline
        !          1035: #Symbol & Example & Explanation \\ \hline
        !          1036: #\verb~**~ & \verb~a**b~ & exponentiation\\
        !          1037: #\verb~*~ & \verb~a*b~ & multiplication\\
        !          1038: #\verb~/~ & \verb~a/b~ & division\\
        !          1039: #\verb~%~ & \verb~a%b~ & * modulo\\
        !          1040: #\verb~+~ & \verb~a+b~ & addition\\
        !          1041: #\verb~-~ & \verb~a-b~ & subtraction\\
        !          1042: #\verb~==~ & \verb~a==b~ & equality\\
        !          1043: #\verb~!=~ & \verb~a!=b~ & inequality\\
        !          1044: #\verb~<~ & \verb~a<b~ & less than\\
        !          1045: #\verb~<=~ & \verb~a<=b~ & less than or equal to\\
        !          1046: #\verb~>~ & \verb~a>b~ & greater than\\
        !          1047: #\verb~>=~ & \verb~a>=b~ & greater than or equal to\\
        !          1048: #\verb~&~ & \verb~a&b~ & * bitwise AND\\
        !          1049: #\verb~^~ & \verb~a^b~ & * bitwise exclusive OR\\
        !          1050: #\verb~|~ & \verb~a|b~ & * bitwise inclusive OR\\
        !          1051: #\verb~&&~ & \verb~a&&b~ & * logical AND\\
        !          1052: #\verb~||~ & \verb~a||b~ & * logical OR\\
        !          1053: %c c l .
        !          1054: %Symbol@Example@Explanation
        !          1055: %_
        !          1056: %**@a**b@exponentiation
        !          1057: %*@a*b@multiplication
        !          1058: %/@a/b@division
        !          1059: %%@a%b@* modulo
        !          1060: %+@a+b@addition
        !          1061: %-@a-b@subtraction
        !          1062: %==@a==b@equality
        !          1063: %!=@a!=b@inequality
        !          1064: %<@a<b@less than
        !          1065: %<=@a<=b@less than or equal to
        !          1066: %>@a>b@greater than
        !          1067: %>=@a>=b@greater than or equal to
        !          1068: %&@a&b@* bitwise AND
        !          1069: %^@a^b@* bitwise exclusive OR
        !          1070: %|@a|b@* bitwise inclusive OR
        !          1071: %&&@a&&b@* logical AND
        !          1072: %||@a||b@* logical OR
        !          1073:
        !          1074: @end table
        !          1075:  (*) Starred explanations indicate that the operator requires integer
        !          1076:  arguments.
        !          1077:
        !          1078:  Logical AND (&&) and OR (||) short-circuit the way they do in C.  That is,
        !          1079:  the second `&&` operand is not evaluated if the first is false; the second
        !          1080:  `||` operand is not evaluated if the first is true.
        !          1081: 4 Ternary
        !          1082: ?expressions operators ternary
        !          1083: ?operators ternary
        !          1084: ?ternary
        !          1085:  There is a single ternary operator:
        !          1086:
        !          1087: @start table - first is interactive cleartext form
        !          1088:      Symbol       Example      Explanation
        !          1089:        ?:          a?b:c     ternary operation
        !          1090: #\begin{tabular}{|ccl|} \hline
        !          1091: #\multicolumn{3}{|c|}{Ternary Operator} \\ \hline \hline
        !          1092: #Symbol & Example & Explanation \\ \hline
        !          1093: #\verb~?:~ & \verb~a?b:c~ & ternary operation\\
        !          1094: %c c l .
        !          1095: %Symbol@Example@Explanation
        !          1096: %_
        !          1097: %?:@a?b:c@* ternary operation
        !          1098:
        !          1099: @end table
        !          1100:  The ternary operator behaves as it does in C.  The first argument (a), which
        !          1101:  must be an integer, is evaluated.  If it is true (non-zero), the second
        !          1102:  argument (b) is evaluated and returned; otherwise the third argument (c) is
        !          1103:  evaluated and returned.
        !          1104:
        !          1105:  The ternary operator is very useful both in constructing piecewise functions
        !          1106:  and in plotting points only when certain conditions are met.
        !          1107:
        !          1108:  Examples:
        !          1109:
        !          1110:  Plot a function that is to equal sin(x) for 0 <= x < 1, 1/x for 1 <= x < 2,
        !          1111:  and undefined elsewhere:
        !          1112:        f(x) = 0<=x && x<1 ? sin(x) : 1<=x && x<2 ? 1/x : 1/0
        !          1113:        plot f(x)
        !          1114: ^ <img align=bottom src="http://www.nas.nasa.gov/~woo/gnuplot/doc/ternary.gif" alt="[ternary.gif]" width=640 height=480>
        !          1115:  Note that `gnuplot` quietly ignores undefined values, so the final branch of
        !          1116:  the function (1/0) will produce no plottable points.  Note also that f(x)
        !          1117:  will be plotted as a continuous function across the discontinuity if a line
        !          1118:  style is used.  To plot it discontinuously, create separate functions for the
        !          1119:  two pieces.  (Parametric functions are also useful for this purpose.)
        !          1120:
        !          1121:  For data in a file, plot the average of the data in columns 2 and 3 against
        !          1122:  the datum in column 1, but only if the datum in column 4 is non-negative:
        !          1123:
        !          1124:        plot 'file' using 1:( $4<0 ? 1/0 : ($2+$3)/2 )
        !          1125:
        !          1126:  Please see `plot data-file using` for an explanation of the `using` syntax.
        !          1127: 3 User-defined
        !          1128: ?expressions user-defined
        !          1129: ?user-defined
        !          1130: ?variables
        !          1131:  New user-defined variables and functions of one through five variables may
        !          1132:  be declared and used anywhere, including on the `plot` command itself.
        !          1133:
        !          1134:  User-defined function syntax:
        !          1135:        <func-name>( <dummy1> {,<dummy2>} ... {,<dummy5>} ) = <expression>
        !          1136:
        !          1137:  where <expression> is defined in terms of <dummy1> through <dummy5>.
        !          1138:
        !          1139:  User-defined variable syntax:
        !          1140:        <variable-name> = <constant-expression>
        !          1141:
        !          1142:  Examples:
        !          1143:        w = 2
        !          1144:        q = floor(tan(pi/2 - 0.1))
        !          1145:        f(x) = sin(w*x)
        !          1146:        sinc(x) = sin(pi*x)/(pi*x)
        !          1147:        delta(t) = (t == 0)
        !          1148:        ramp(t) = (t > 0) ? t : 0
        !          1149:        min(a,b) = (a < b) ? a : b
        !          1150:        comb(n,k) = n!/(k!*(n-k)!)
        !          1151:        len3d(x,y,z) = sqrt(x*x+y*y+z*z)
        !          1152:        plot f(x) = sin(x*a), a = 0.2, f(x), a = 0.4, f(x)
        !          1153:
        !          1154: ^ <img align=bottom src="http://www.nas.nasa.gov/~woo/gnuplot/doc/userdefined.gif" alt="[userdefined.gif]" width=640 height=480>
        !          1155:  Note that the variable `pi` is already defined.  But it is in no way magic;
        !          1156:  you may redefine it to be whatever you like.
        !          1157:
        !          1158:  Valid names are the same as in most programming languages: they must begin
        !          1159:  with a letter, but subsequent characters may be letters, digits, "$", or "_".
        !          1160:  Note, however, that the `fit` mechanism uses several variables with names
        !          1161:  that begin "FIT_".  It is safest to avoid using such names.  "FIT_LIMIT",
        !          1162:  however, is one that you may wish to redefine. See the documentation
        !          1163:  on `fit` for details.
        !          1164:
        !          1165:
        !          1166:  See `show functions`, `show variables`, and `fit`.
        !          1167: 2 Glossary
        !          1168: ?glossary
        !          1169:  Throughout this document an attempt has been made to maintain consistency of
        !          1170:  nomenclature.  This cannot be wholly successful because as `gnuplot` has
        !          1171:  evolved over time, certain command and keyword names have been adopted that
        !          1172:  preclude such perfection.  This section contains explanations of the way
        !          1173:  some of these terms are used.
        !          1174:
        !          1175:  A "page" or "screen" is the entire area addressable by `gnuplot`.  On a
        !          1176:  monitor, it is the full screen; on a plotter, it is a single sheet of paper.
        !          1177:
        !          1178:  A screen may contain one or more "plots".  A plot is defined by an abscissa
        !          1179:  and an ordinate, although these need not actually appear on it, as well as
        !          1180:  the margins and any text written therein.
        !          1181:
        !          1182:  A plot contains one "graph".  A graph is defined by an abscissa and an
        !          1183:  ordinate, although these need not actually appear on it.
        !          1184:
        !          1185:  A graph may contain one or more "lines".  A line is a single function or
        !          1186:  data set.  "Line" is also a plotting style.  The word will also be used in
        !          1187:  sense "a line of text".  Presumably the context will remove any ambiguity.
        !          1188:
        !          1189:  The lines on a graph may have individual names.  These may be listed
        !          1190:  together with a sample of the plotting style used to represent them in
        !          1191:  the "key", sometimes also called the "legend".
        !          1192:
        !          1193:  The word "title" occurs with multiple meanings in `gnuplot`.  In this
        !          1194:  document, it will always be preceded by the adjective "plot", "line", or
        !          1195:  "key" to differentiate among them.
        !          1196:
        !          1197:  A graph may have up to four labelled axes.  Various commands have the name of
        !          1198:  an axis built into their names, such as `set xlabel`.  Other commands have
        !          1199:  one or more axis names as options, such as `set logscale xy`.  The names of
        !          1200:  the four axes for these usages are "x" for the axis along the bottom border
        !          1201:  of the plot, "y" for the left border, "x2" for the top border, and "y2" for
        !          1202:  the right border.  "z" also occurs in commands used with 3-d plotting.
        !          1203:
        !          1204:  When discussing data files, the term "record" will be resurrected and used
        !          1205:  to denote a single line of text in the file, that is, the characters between
        !          1206:  newline or end-of-record characters.  A "point" is the datum extracted from
        !          1207:  a single record.  A "datablock" is a set of points from consecutive records,
        !          1208:  delimited by blank records.  A line, when referred to in the context of a
        !          1209:  data file, is a subset of a datablock.
        !          1210: 2 Plotting
        !          1211: ?plotting
        !          1212:  There are three `gnuplot` commands which actually create a plot: `plot`,
        !          1213:  `splot` and `replot`.  `plot` generates 2-d plots, `splot` generates 3-d
        !          1214:  plots (actually 2-d projections, of course), and `replot` appends its
        !          1215:  arguments to the previous `plot` or `splot` and executes the modified
        !          1216:  command.
        !          1217:
        !          1218:  Much of the general information about plotting can be found in the discussion
        !          1219:  of `plot`; information specific to 3-d can be found in the `splot` section.
        !          1220:
        !          1221:  `plot` operates in either rectangular or polar coordinates -- see `set polar`
        !          1222:  for details of the latter.  `splot` operates only in rectangular coordinates,
        !          1223:  but the `set mapping` command allows for a few other coordinate systems to be
        !          1224:  treated.  In addition, the `using` option allows both `plot` and `splot` to
        !          1225:  treat almost any coordinate system you'd care to define.
        !          1226:
        !          1227:  `splot` can plot surfaces and contours in addition to points and/or lines.
        !          1228:  In addition to `splot`, see `set isosamples` for information about defining
        !          1229:  the grid for a 3-d function;  `splot datafile` for information about the
        !          1230:  requisite file structure for 3-d data values; and `set contour` and `set
        !          1231:  cntrparam` for information about contours.
        !          1232: 2 Start-up
        !          1233: ?startup
        !          1234: ?start
        !          1235: ?.gnuplot
        !          1236:  When `gnuplot` is run, it looks for an initialization file to load.  This
        !          1237:  file is called `.gnuplot` on Unix and AmigaOS systems, and `GNUPLOT.INI` on
        !          1238:  other systems.  If this file is not found in the current directory, the
        !          1239:  program will look for it in the home directory (under AmigaOS,
        !          1240:  Atari(single)TOS, MS-DOS and OS/2, the environment variable `gnuplot` should
        !          1241:  contain the name of this directory).  Note: if NOCWDRC is defined during the
        !          1242:  installation, `gnuplot` will not read from the current directory.
        !          1243:
        !          1244:  If the initialization file is found, `gnuplot` executes the commands in it.
        !          1245:  These may be any legal `gnuplot` commands, but typically they are limited to
        !          1246:  setting the terminal and defining frequently-used functions or variables.
        !          1247: 2 Substitution
        !          1248: ?substitution
        !          1249:  Command-line substitution is specified by a system command enclosed in
        !          1250:  backquotes.  This command is spawned and the output it produces replaces
        !          1251:  the name of the command (and backquotes) on the command line.  Some
        !          1252:  implementations also support pipes;  see `plot data-file special-filenames`.
        !          1253:
        !          1254:  Newlines in the output produced by the spawned command are replaced with
        !          1255:  blanks.
        !          1256:
        !          1257:  Command-line substitution can be used anywhere on the `gnuplot` command
        !          1258:  line.
        !          1259:
        !          1260:  Example:
        !          1261:
        !          1262:  This will run the program `leastsq` and replace `leastsq` (including
        !          1263:  backquotes) on the command line with its output:
        !          1264:        f(x) = `leastsq`
        !          1265:
        !          1266:  or, in VMS
        !          1267:        f(x) = `run leastsq`
        !          1268: 2 Syntax
        !          1269: ?syntax
        !          1270: ?specify
        !          1271: ?punctuation
        !          1272:  The general rules of syntax and punctuation in `gnuplot` are that keywords
        !          1273:  and options are order-dependent.  Options and any accompanying parameters are
        !          1274:  separated by spaces whereas lists and coordinates are separated by commas.
        !          1275:  Ranges are separated by colons and enclosed in brackets [], text and file
        !          1276:  names are enclosed in quotes, and a few miscellaneous things are enclosed
        !          1277:  in parentheses.  Braces {} are used for a few special purposes.
        !          1278:
        !          1279:  Commas are used to separate coordinates on the `set` commands `arrow`,
        !          1280:  `key`, and `label`; the list of variables being fitted (the list after the
        !          1281:  `via` keyword on the `fit` command); lists of discrete contours or the loop
        !          1282:  parameters which specify them on the `set cntrparam` command; the arguments
        !          1283:  of the `set` commands `dgrid3d`, `dummy`, `isosamples`, `offsets`, `origin`,
        !          1284:  `samples`, `size`, `time`, and `view`; lists of tics or the loop parameters
        !          1285:  which specify them; the offsets for titles and axis labels; parametric
        !          1286:  functions to be used to calculate the x, y, and z coordinates on the `plot`,
        !          1287:  `replot` and `splot` commands; and the complete sets of keywords specifying
        !          1288:  individual plots (data sets or functions) on the `plot`, `replot` and `splot`
        !          1289:  commands.
        !          1290:
        !          1291:  Parentheses are used to delimit sets of explicit tics (as opposed to loop
        !          1292:  parameters) and to indicate computations in the `using` filter of the `fit`,
        !          1293:  `plot`, `replot` and `splot` commands.
        !          1294:
        !          1295:  (Parentheses and commas are also used as usual in function notation.)
        !          1296:
        !          1297:  Brackets are used to delimit ranges, whether they are given on `set`, `plot`
        !          1298:  or `splot` commands.
        !          1299:
        !          1300:  Colons are used to separate extrema in `range` specifications (whether they
        !          1301:  are given on `set`, `plot` or `splot` commands) and to separate entries in
        !          1302:  the `using` filter of the `plot`, `replot`, `splot` and `fit` commands.
        !          1303:
        !          1304:  Semicolons are used to separate commands given on a single command line.
        !          1305:
        !          1306:  Braces are used in text to be specially processed by some terminals, like
        !          1307:  `postscript`.  They are also used to denote complex numbers: {3,2} = 3 + 2i.
        !          1308:
        !          1309:  Text may be enclosed in single- or double-quotes.  Backslash processing of
        !          1310:  sequences like \n (newline) and \345 (octal character code) is performed for
        !          1311:  double-quoted strings, but not for single-quoted strings.
        !          1312:
        !          1313:  The justification is the same for each line of a multi-line string.  Thus the
        !          1314:  center-justified string
        !          1315:        "This is the first line of text.\nThis is the second line."
        !          1316:  will produce
        !          1317:                         This is the first line of text.
        !          1318:                            This is the second line.
        !          1319:  but
        !          1320:        'This is the first line of text.\nThis is the second line.'
        !          1321:  will produce
        !          1322:            This is the first line of text.\nThis is the second line.
        !          1323:
        !          1324:  Filenames may be entered with either single- or double-quotes.  In this
        !          1325:  manual the command examples generally single-quote filenames and double-quote
        !          1326:  other string tokens for clarity.
        !          1327:
        !          1328:  At present you should not embed \n inside {} when using the enhanced option
        !          1329:  of the postscript terminal.
        !          1330:
        !          1331:  The EEPIC, Imagen, Uniplex, LaTeX, and TPIC drivers allow a newline to be
        !          1332:  specified by \\ in a single-quoted string or \\\\ in a double-quoted string.
        !          1333:
        !          1334:  Back-quotes are used to enclose system commands for substitution.
        !          1335: 2 Time/Date data
        !          1336: ?time/date
        !          1337:  `gnuplot` supports the use of time and/or date information as input data.
        !          1338:  This feature is activated by the commands `set xdata time`, `set ydata time`,
        !          1339:  etc.
        !          1340:
        !          1341:  Internally all times and dates are converted to the number of seconds from
        !          1342:  the year 2000.  The command `set timefmt` defines the format for all inputs:
        !          1343:  data files, ranges, tics, label positions---in short, anything that accepts a
        !          1344:  data value must receive it in this format.  Since only one input format can
        !          1345:  be in force at a given time, all time/date quantities being input at the same
        !          1346:  time must be presented in the same format.  Thus if both x and y data in a
        !          1347:  file are time/date, they must be in the same format.
        !          1348:
        !          1349:  The conversion to and from seconds assumes Universal Time (which is the same
        !          1350:  as Greenwich Standard Time).  There is no provision for changing the time
        !          1351:  zone or for daylight savings.  If all your data refer to the same time zone
        !          1352:  (and are all either daylight or standard) you don't need to worry about these
        !          1353:  things.  But if the absolute time is crucial for your application, you'll
        !          1354:  need to convert to UT yourself.
        !          1355:
        !          1356:  Commands like `show xrange` will re-interpret the integer according to
        !          1357:  `timefmt`.  If you change `timefmt`, and then `show` the quantity again, it
        !          1358:  will be displayed in the new `timefmt`.  For that matter, if you give the
        !          1359:  deactivation command (like `set xdata`), the quantity will be shown in its
        !          1360:  numerical form.
        !          1361:
        !          1362:  The command `set format` defines the format that will be used for tic labels,
        !          1363:  whether or not the specified axis is time/date.
        !          1364:
        !          1365:  If time/date information is to be plotted from a file, the `using` option
        !          1366:  _must_ be used on the `plot` or `splot` command.  These commands simply use
        !          1367:  white space to separate columns, but white space may be embedded within the
        !          1368:  time/date string.  If you use tabs as a separator, some trial-and-error may
        !          1369:  be necessary to discover how your system treats them.
        !          1370:
        !          1371:  The following example demonstrates time/date plotting.
        !          1372:
        !          1373:  Suppose the file "data" contains records like
        !          1374:
        !          1375:        03/21/95 10:00  6.02e23
        !          1376:
        !          1377:  This file can be plotted by
        !          1378:
        !          1379:        set xdata time
        !          1380:        set timefmt "%m/%d/%y"
        !          1381:        set xrange ["03/21/95":"03/22/95"]
        !          1382:        set format x "%m/%d"
        !          1383:        set timefmt "%m/%d/%y %H:%M"
        !          1384:        plot "data" using 1:3
        !          1385:
        !          1386:  which will produce xtic labels that look like "03/21".
        !          1387:
        !          1388:  See the descriptions of each command for more details.
        !          1389: 1 Commands
        !          1390: ?commands
        !          1391:  This section lists the commands acceptable to `gnuplot` in alphabetical
        !          1392:  order.  Printed versions of this document contain all commands; on-line
        !          1393:  versions may not be complete.  Indeed, on some systems there may be no
        !          1394:  commands at all listed under this heading.
        !          1395:
        !          1396:  Note that in most cases unambiguous abbreviations for command names and their
        !          1397:  options are permissible, i.e., "`p f(x) w l`" instead of "`plot f(x) with
        !          1398:  lines`".
        !          1399:
        !          1400:  In the syntax descriptions, braces ({}) denote optional arguments and a
        !          1401:  vertical bar (|) separates mutually exclusive choices.
        !          1402: 2 cd
        !          1403: ?commands cd
        !          1404: ?cd
        !          1405:  The `cd` command changes the working directory.
        !          1406:
        !          1407:  Syntax:
        !          1408:        cd '<directory-name>'
        !          1409:
        !          1410:  The directory name must be enclosed in quotes.
        !          1411:
        !          1412:  Examples:
        !          1413:        cd 'subdir'
        !          1414:        cd ".."
        !          1415:
        !          1416:  DOS users _must_ use single-quotes---backslash [\] has special significance
        !          1417:  inside double-quotes.  For example,
        !          1418:        cd "c:\newdata"
        !          1419:  fails, but
        !          1420:        cd 'c:\newdata'
        !          1421:  works as expected.
        !          1422: 2 call
        !          1423: ?commands call
        !          1424: ?call
        !          1425:  The `call` command is identical to the load command with one exception: you
        !          1426:  can have up to ten additional parameters to the command (delimited according
        !          1427:  to the standard parser rules) which can be substituted into the lines read
        !          1428:  from the file.  As each line is read from the `call`ed input file, it is
        !          1429:  scanned for the sequence `$` (dollar-sign) followed by a digit (0--9).  If
        !          1430:  found, the sequence is replaced by the corresponding parameter from the
        !          1431:  `call` command line.  If the parameter was specified as a string in the
        !          1432:  `call` line, it is substituted without its enclosing quotes.  `$` followed by
        !          1433:  any character other than a digit will be that character.  E.g. use `$$` to
        !          1434:  get a single `$`.  Providing more than ten parameters on the `call` command
        !          1435:  line will cause an error.  A parameter that was not provided substitutes as
        !          1436:  nothing.  Files being `call`ed may themselves contain `call` or `load`
        !          1437:  commands.
        !          1438:
        !          1439:  The `call` command _must_ be the last command on a multi-command line.
        !          1440:
        !          1441:  Syntax:
        !          1442:        call "<input-file>" <parameter-0> <parm-1> ... <parm-9>
        !          1443:
        !          1444:  The name of the input file must be enclosed in quotes, and it is recommended
        !          1445:  that parameters are similarly enclosed in quotes (future versions of gnuplot
        !          1446:  may treat quoted and unquoted arguments differently).
        !          1447:
        !          1448:  Example:
        !          1449:
        !          1450:  If the file 'calltest.gp' contains the line:
        !          1451:        print "p0=$0 p1=$1 p2=$2 p3=$3 p4=$4 p5=$5 p6=$6 p7=x$7x"
        !          1452:
        !          1453:  entering the command:
        !          1454:        call 'calltest.gp' "abcd" 1.2 + "'quoted'" -- "$2"
        !          1455:
        !          1456:  will display:
        !          1457:        p0=abcd p1=1.2 p2=+ p3='quoted' p4=- p5=- p6=$2 p7=xx
        !          1458:
        !          1459:  NOTE: there is a clash in syntax with the datafile `using` callback
        !          1460:  operator.  Use `$$n` or `column(n)` to access column n from a datafile inside
        !          1461:  a `call`ed datafile plot.
        !          1462: 2 clear
        !          1463: ?commands clear
        !          1464: ?clear
        !          1465:  The `clear` command erases the current screen or output device as specified
        !          1466:  by `set output`.  This usually generates a formfeed on hardcopy devices.  Use
        !          1467:  `set terminal` to set the device type.
        !          1468:
        !          1469:  For some terminals `clear` erases only the portion of the plotting surface
        !          1470:  defined by `set size`, so for these it can be used in conjunction with `set
        !          1471:  multiplot` to create an inset.
        !          1472:
        !          1473:  Example:
        !          1474:        set multiplot
        !          1475:        plot sin(x)
        !          1476:        set origin 0.5,0.5
        !          1477:        set size 0.4,0.4
        !          1478:        clear
        !          1479:        plot cos(x)
        !          1480:        set nomultiplot
        !          1481:
        !          1482:  Please see `set multiplot`, `set size`, and `set origin` for details of these
        !          1483:  commands.
        !          1484: 2 exit
        !          1485: ?commands exit
        !          1486: ?exit
        !          1487:  The commands `exit` and `quit` and the END-OF-FILE character will exit the
        !          1488:  current `gnuplot` command file and `load` the next one.  See "help
        !          1489:  batch/interactive" for more details.
        !          1490:
        !          1491:  Each of these commands will clear the output device (as does the `clear`
        !          1492:  command) before exiting.
        !          1493: 2 fit
        !          1494: ?commands fit
        !          1495: ?fit
        !          1496: ?least-squares
        !          1497: ?Marquardt
        !          1498:  The `fit` command can fit a user-defined function to a set of data points
        !          1499:  (x,y) or (x,y,z), using an implementation of the nonlinear least-squares
        !          1500:  (NLLS) Marquardt-Levenberg algorithm.  Any user-defined variable occurring in
        !          1501:  the function body may serve as a fit parameter, but the return type of the
        !          1502:  function must be real.
        !          1503:
        !          1504:  Syntax:
        !          1505:        fit {[xrange] {[yrange]}} <function> '<datafile>'
        !          1506:            {datafile-modifiers}
        !          1507:            via '<parameter file>' | <var1>{,<var2>,...}
        !          1508:
        !          1509:  Ranges may be specified to temporarily limit the data which is to be fitted;
        !          1510:  any out-of-range data points are ignored. The syntax is
        !          1511:        [{dummy_variable=}{<min>}{:<max>}],
        !          1512:  analogous to `plot`; see `plot ranges`.
        !          1513:
        !          1514:  <function> is any valid `gnuplot` expression, although it is usual to use a
        !          1515:  previously user-defined function of the form f(x) or f(x,y).
        !          1516:
        !          1517:  <datafile> is treated as in the `plot` command.  All the `plot datafile`
        !          1518:  modifiers (`using`, `every`,...) except `smooth` are applicable to `fit`.
        !          1519:  See `plot datafile`.
        !          1520:
        !          1521:  The default data formats for fitting functions with a single independent
        !          1522:  variable, y=f(x), are {x:}y or x:y:s; those formats can be changed with
        !          1523:  the datafile `using` qualifier.  The third item, (a column number or an
        !          1524:  expression), if present, is interpreted as the standard deviation of the
        !          1525:  corresponding y value and is used to compute a weight for the datum, 1/s**2.
        !          1526:  Otherwise, all data points are weighted equally, with a weight of one.
        !          1527:
        !          1528:  To fit a function with two independent variables, z=f(x,y), the required
        !          1529:  format is `using` with four items, x:y:z:s.  The complete format must be
        !          1530:  given---no default columns are assumed for a missing token.  Weights for
        !          1531:  each data point are evaluated from 's' as above.  If error estimates are
        !          1532:  not available, a constant value can be specified as a constant expression
        !          1533:  (see `plot datafile using`), e.g., `using 1:2:3:(1)`.
        !          1534:
        !          1535:  Multiple datasets may be simultaneously fit with functions of one
        !          1536:  independent variable by making y a 'pseudo-variable', e.g., the dataline
        !          1537:  number, and fitting as two independent variables.  See `fit multibranch`.
        !          1538:
        !          1539:  The `via` qualifier specifies which parameters are to be adjusted, either
        !          1540:  directly, or by referencing a parameter file.
        !          1541:
        !          1542:  Examples:
        !          1543:        f(x) = a*x**2 + b*x + c
        !          1544:        g(x,y) = a*x**2 + b*y**2 + c*x*y
        !          1545:        FIT_LIMIT = 1e-6
        !          1546:        fit f(x) 'measured.dat' via 'start.par'
        !          1547:        fit f(x) 'measured.dat' using 3:($7-5) via 'start.par'
        !          1548:        fit f(x) './data/trash.dat' using 1:2:3 via a, b, c
        !          1549:        fit g(x,y) 'surface.dat' using 1:2:3:(1) via a, b, c
        !          1550:
        !          1551:  After each iteration step, detailed information about the current state
        !          1552:  of the fit is written to the display.  The same information about the
        !          1553:  initial and final states is written to a log file, "fit.log".  This file
        !          1554:  is always appended to, so as to not lose any previous fit history;  it
        !          1555:  should be deleted or renamed as desired.
        !          1556:
        !          1557:  The fit may be interrupted by pressing Ctrl-C (any key but Ctrl-C under
        !          1558:  MSDOS and Atari Multitasking Systems).  After the current iteration
        !          1559:  completes, you have the option to (1) stop the fit and accept the current
        !          1560:  parameter values, (2) continue the fit, (3) execute a `gnuplot` command
        !          1561:  as specified by the environment variable FIT_SCRIPT.  The default for
        !          1562:  FIT_SCRIPT is `replot`, so if you had previously plotted both the data
        !          1563:  and the fitting function in one graph, you can display the current state
        !          1564:  of the fit.
        !          1565:
        !          1566:  Once `fit` has finished, the `update` command may be used to store final
        !          1567:  values in a file for subsequent use as a parameter file.   See `update`
        !          1568:  for details.
        !          1569: 3 adjustable parameters
        !          1570: ?commands fit parameters
        !          1571: ?fit parameters
        !          1572: ?commands fit adjustable_parameters
        !          1573: ?fit adjustable_parameters
        !          1574: ?fit_parameters
        !          1575:  There are two ways that `via` can specify the parameters to be adjusted,
        !          1576:  either directly on the command line or indirectly, by referencing a
        !          1577:  parameter file.  The two use different means to set initial values.
        !          1578:
        !          1579:  Adjustable parameters can be specified by a comma-separated list of variable
        !          1580:  names after the `via` keyword.  Any variable that is not already defined is
        !          1581:  is created with an initial value of 1.0.  However, the fit is more likely
        !          1582:  to converge rapidly if the variables have been previously declared with more
        !          1583:  appropriate starting values.
        !          1584:
        !          1585:  In a parameter file, each parameter to be varied and a corresponding initial
        !          1586:  value are specified, one per line, in the form
        !          1587:        varname = value
        !          1588:
        !          1589:  Comments, marked by '#', and blank lines are permissible.  The
        !          1590:  special form
        !          1591:        varname = value       # FIXED
        !          1592:
        !          1593:  means that the variable is treated as a 'fixed parameter', initialized by the
        !          1594:  parameter file, but not adjusted by `fit`.  For clarity, it may be useful to
        !          1595:  designate variables as fixed parameters so that their values are reported by
        !          1596:  `fit`.  The keyword `# FIXED` has to appear in exactly this form.
        !          1597:
        !          1598: 3 beginner's guide
        !          1599: ?commands fit beginners_guide
        !          1600: ?fit beginners_guide
        !          1601: ?fit guide
        !          1602: ?fitting
        !          1603:  `fit` is used to find a set of parameters that 'best' fits your data to your
        !          1604:  user-defined function.  The fit is judged on the basis of the the sum of the
        !          1605:  squared differences or 'residuals' (SSR) between the input data points and
        !          1606:  the function values, evaluated at the same places.  This quantity is often
        !          1607:  called 'chisquare' (i.e., the Greek letter chi, to the power of 2).  The
        !          1608:  algorithm attempts to minimize SSR, or more precisely, WSSR, as the residuals
        !          1609:  are 'weighted' by the input data errors (or 1.0) before being squared; see
        !          1610:  `fit error_estimates` for details.
        !          1611:
        !          1612:  That's why it is called 'least-squares fitting'.  Let's look at an example
        !          1613:  to see what is meant by 'non-linear', but first we had better go over some
        !          1614:  terms.  Here it is convenient to use z as the dependent variable for
        !          1615:  user-defined functions of either one independent variable, z=f(x), or two
        !          1616:  independent variables, z=f(x,y).  A parameter is a user-defined variable
        !          1617:  that `fit` will adjust, i.e., an unknown quantity in the function
        !          1618:  declaration.  Linearity/non-linearity refers to the relationship of the
        !          1619:  dependent variable, z, to the parameters which `fit` is adjusting, not of
        !          1620:  z to the independent variables, x and/or y.  (To be technical, the
        !          1621:  second {and higher} derivatives of the fitting function with respect to
        !          1622:  the parameters are zero for a linear least-squares problem).
        !          1623:
        !          1624:  For linear least-squares (LLS), the user-defined function will be a sum of
        !          1625:  simple functions, not involving any parameters, each multiplied by one
        !          1626:  parameter.  NLLS handles more complicated functions in which parameters can
        !          1627:  be used in a large number of ways.  An example that illustrates the
        !          1628:  difference between linear and nonlinear least-squares is the Fourier series.
        !          1629:  One member may be written as
        !          1630:       z=a*sin(c*x) + b*cos(c*x).
        !          1631:  If a and b are the unknown parameters and c is constant, then estimating
        !          1632:  values of the parameters is a linear least-squares problem.  However, if
        !          1633:  c is an unknown parameter, the problem is nonlinear.
        !          1634:
        !          1635:  In the linear case, parameter values can be determined by comparatively
        !          1636:  simple linear algebra, in one direct step.  However LLS is a special case
        !          1637:  which is also solved along with more general NLLS problems by the iterative
        !          1638:  procedure that `gnuplot` uses.  `fit` attempts to find the minimum by doing
        !          1639:  a search.  Each step (iteration) calculates WSSR with a new set of parameter
        !          1640:  values.  The Marquardt-Levenberg algorithm selects the parameter values for
        !          1641:  the next iteration.  The process continues until a preset criterium is met,
        !          1642:  either (1) the fit has "converged" (the relative change in WSSR is less than
        !          1643:  FIT_LIMIT), or (2) it reaches a preset iteration count limit, FIT_MAXITER
        !          1644:  (see `fit control variables`).  The fit may also be interrupted
        !          1645:  and subsequently halted from the keyboard (see `fit`).
        !          1646:
        !          1647:  Often the function to be fitted will be based on a model (or theory) that
        !          1648:  attempts to describe or predict the behaviour of the data.  Then `fit` can
        !          1649:  be used to find values for the free parameters of the model, to determine
        !          1650:  how well the data fits the model, and to estimate an error range for each
        !          1651:  parameter.  See `fit error_estimates`.
        !          1652:
        !          1653:  Alternatively, in curve-fitting, functions are selected independent of
        !          1654:  a model (on the basis of experience as to which are likely to describe
        !          1655:  the trend of the data with the desired resolution and a minimum number
        !          1656:  of parameters*functions.)  The `fit` solution then provides an analytic
        !          1657:  representation of the curve.
        !          1658:
        !          1659:  However, if all you really want is a smooth curve through your data points,
        !          1660:  the `smooth` option to `plot` may be what you've been looking for rather
        !          1661:  than `fit`.
        !          1662: 3 error estimates
        !          1663: ?commands fit error_estimate
        !          1664: ?fit error_estimate
        !          1665: ?fit errors
        !          1666:  In `fit`, the term "error" is used in two different contexts, data error
        !          1667:  estimates and parameter error estimates.
        !          1668:
        !          1669:  Data error estimates are used to calculate the relative weight of each data
        !          1670:  point when determining the weighted sum of squared residuals, WSSR or
        !          1671:  chisquare.  They can affect the parameter estimates, since they determine
        !          1672:  how much influence the deviation of each data point from the fitted function
        !          1673:  has on the final values.  Some of the `fit` output information, including
        !          1674:  the parameter error estimates, is more meaningful if accurate data error
        !          1675:  estimates have been provided.
        !          1676:
        !          1677:  The 'statistical overview' describes some of the `fit` output and gives some
        !          1678:  background for the 'practical guidelines'.
        !          1679: 4 statistical overview
        !          1680: ?commands fit error statistical_overview
        !          1681: ?fit error statistical_overview
        !          1682: ?statistical_overview
        !          1683:  The theory of non-linear least-squares (NLLS) is generally described in terms
        !          1684:  of a normal distribution of errors, that is, the input data is assumed to be
        !          1685:  a sample from a population having a given mean and a Gaussian (normal)
        !          1686:  distribution about the mean with a given standard deviation.  For a sample of
        !          1687:  sufficiently large size, and knowing the population standard deviation, one
        !          1688:  can use the statistics of the chisquare distribution to describe a "goodness
        !          1689:  of fit" by looking at the variable often called "chisquare".  Here, it is
        !          1690:  sufficient to say that a reduced chisquare (chisquare/degrees of freedom,
        !          1691:  where degrees of freedom is the number of datapoints less the number of
        !          1692:  parameters being fitted) of 1.0 is an indication that the weighted sum of
        !          1693:  squared deviations between the fitted function and the data points is the
        !          1694:  same as that expected for a random sample from a population characterized by
        !          1695:  the function with the current value of the parameters and the given standard
        !          1696:  deviations.
        !          1697:
        !          1698:  If the standard deviation for the population is not constant, as in counting
        !          1699:  statistics where variance = counts, then each point should be individually
        !          1700:  weighted when comparing the observed sum of deviations and the expected sum
        !          1701:  of deviations.
        !          1702:
        !          1703:  At the conclusion `fit` reports 'stdfit', the standard deviation of the fit,
        !          1704:  which is the rms of the residuals, and the variance of the residuals, also
        !          1705:  called 'reduced chisquare' when the data points are weighted.  The number of
        !          1706:  degrees of freedom (the number of data points minus the number of fitted
        !          1707:  parameters) is used in these estimates because the parameters used in
        !          1708:  calculating the residuals of the datapoints were obtained from the same data.
        !          1709:
        !          1710:  To estimate confidence levels for the parameters, one can use the minimum
        !          1711:  chisquare obtained from the fit and chisquare statistics to determine the
        !          1712:  value of chisquare corresponding to the desired confidence level, but
        !          1713:  considerably more calculation is required to determine the combinations of
        !          1714:  parameters which produce such values.
        !          1715:
        !          1716:  Rather than determine confidence intervals, `fit` reports parameter error
        !          1717:  estimates which are readily obtained from the variance-covariance matrix
        !          1718:  after the final iteration.  By convention, these estimates are called
        !          1719:  "standard errors" or "asymptotic standard errors", since they are calculated
        !          1720:  in the same way as the standard errors (standard deviation of each parameter)
        !          1721:  of a linear least-squares problem, even though the statistical conditions for
        !          1722:  designating the quantity calculated to be a standard deviation are not
        !          1723:  generally valid for the NLLS problem.  The asymptotic standard errors are
        !          1724:  generally over-optimistic and should not be used for determining confidence
        !          1725:  levels, but are useful for qualitative purposes.
        !          1726:
        !          1727:  The final solution also produces a correlation matrix, which gives an
        !          1728:  indication of the correlation of parameters in the region of the solution;
        !          1729:  if one parameter is changed, increasing chisquare, does changing another
        !          1730:  compensate?  The main diagonal elements, autocorrelation, are all 1; if
        !          1731:  all parameters were independent, all other elements would be nearly 0.  Two
        !          1732:  variables which completely compensate each other would have an off-diagonal
        !          1733:  element of unit magnitude, with a sign depending on whether the relation is
        !          1734:  proportional or inversely proportional.  The smaller the magnitudes of the
        !          1735:  off-diagonal elements, the closer the estimates of the standard deviation
        !          1736:  of each parameter would be to the asymptotic standard error.
        !          1737: 4 practical guidelines
        !          1738: ?commands fit error practical_guidelines
        !          1739: ?fit error practical_guidelines
        !          1740: ?practical_guidelines
        !          1741: ?guidelines
        !          1742:  If you have a basis for assigning weights to each data point, doing so lets
        !          1743:  you make use of additional knowledge about your measurements, e.g., take into
        !          1744:  account that some points may be more reliable than others.  That may affect
        !          1745:  the final values of the parameters.
        !          1746:
        !          1747:  Weighting the data provides a basis for interpreting the additional `fit`
        !          1748:  output after the last iteration.  Even if you weight each point equally,
        !          1749:  estimating an average standard deviation rather than using a weight of 1
        !          1750:  makes WSSR a dimensionless variable, as chisquare is by definition.
        !          1751:
        !          1752:  Each fit iteration will display information which can be used to evaluate
        !          1753:  the progress of the fit.  (An '*' indicates that it did not find a smaller
        !          1754:  WSSR and is trying again.)  The 'sum of squares of residuals', also called
        !          1755:  'chisquare', is the WSSR between the data and your fitted function; `fit`
        !          1756:  has minimized that.  At this stage, with weighted data, chisquare is expected
        !          1757:  to approach the number of degrees of freedom (data points minus parameters).
        !          1758:  The WSSR can be used to calculate the reduced chisquare (WSSR/ndf) or stdfit,
        !          1759:  the standard deviation of the fit, sqrt(WSSR/ndf).  Both of these are
        !          1760:  reported for the final WSSR.
        !          1761:
        !          1762:  If the data are unweighted, stdfit is the rms value of the deviation of the
        !          1763:  data from the fitted function, in user units.
        !          1764:
        !          1765:  If you supplied valid data errors, the number of data points is large enough,
        !          1766:  and the model is correct, the reduced chisquare should be about unity.  (For
        !          1767:  details, look up the 'chi-squared distribution' in your favourite statistics
        !          1768:  reference.)  If so, there are additional tests, beyond the scope of this
        !          1769:  overview, for determining how well the model fits the data.
        !          1770:
        !          1771:  A reduced chisquare much larger than 1.0 may be due to incorrect data error
        !          1772:  estimates, data errors not normally distributed, systematic measurement
        !          1773:  errors, 'outliers', or an incorrect model function.  A plot of the residuals,
        !          1774:  e.g., `plot 'datafile' using 1:($2-f($1))`, may help to show any systematic
        !          1775:  trends.  Plotting both the data points and the function may help to suggest
        !          1776:  another model.
        !          1777:
        !          1778:  Similarly, a reduced chisquare less than 1.0 indicates WSSR is less than that
        !          1779:  expected for a random sample from the function with normally distributed
        !          1780:  errors.  The data error estimates may be too large, the statistical
        !          1781:  assumptions may not be justified, or the model function may be too general,
        !          1782:  fitting fluctuations in a particular sample in addition to the underlying
        !          1783:  trends.  In the latter case, a simpler function may be more appropriate.
        !          1784:
        !          1785:  You'll have to get used to both `fit` and the kind of problems you apply it
        !          1786:  to before you can relate the standard errors to some more practical estimates
        !          1787:  of parameter uncertainties or evaluate the significance of the correlation
        !          1788:  matrix.
        !          1789:
        !          1790:  Note that `fit`, in common with most NLLS implementations, minimizes the
        !          1791:  weighted sum of squared distances (y-f(x))**2.  It does not provide any means
        !          1792:  to account for "errors" in the values of x, only in y.  Also, any "outliers"
        !          1793:  (data points outside the normal distribution of the model) will have an
        !          1794:  exaggerated effect on the solution.
        !          1795: 3 fit controlling
        !          1796: ?commands fit_control
        !          1797: ?fit_control
        !          1798: ?fit control
        !          1799:  There are a number of `gnuplot` variables that can be defined to affect
        !          1800:  `fit`.  Those which can be defined once `gnuplot` is running are listed
        !          1801:  under 'control_variables' while those defined before starting `gnuplot`
        !          1802:  are listed under 'environment_variables'.
        !          1803: 4 control variables
        !          1804: ?commands fit_control variables
        !          1805: ?fit_control variables
        !          1806: ?fit control variables
        !          1807:  The default epsilon limit (1e-5) may be changed by declaring a value for
        !          1808:        FIT_LIMIT
        !          1809:  When the sum of squared residuals changes between two iteration steps by
        !          1810:  a factor less than this number (epsilon), the fit is considered to have
        !          1811:  'converged'.
        !          1812:
        !          1813:  The maximum number of iterations may be limited by declaring a value for
        !          1814:        FIT_MAXITER
        !          1815:  A value of 0 (or not defining it at all)  means that there is no limit.
        !          1816:
        !          1817:  If you need even more control about the algorithm, and know the
        !          1818:  Marquardt-Levenberg algorithm well, there are some more variables to
        !          1819:  influence it. The startup value of `lambda` is normally calculated
        !          1820:  automatically from the ML-matrix, but if you want to, you may provide
        !          1821:  your own one with
        !          1822:        FIT_START_LAMBDA
        !          1823:  Specifying FIT_START_LAMBDA as zero or less will re-enable the automatic
        !          1824:  selection. The variable
        !          1825:        FIT_LAMBDA_FACTOR
        !          1826:  gives the factor by which `lambda` is increased or decreased whenever
        !          1827:  the chi-squared target function increased or decreased significantly.
        !          1828:  Setting FIT_LAMBDA_FACTOR to zero re-enables the default factor of
        !          1829:  10.0.
        !          1830:
        !          1831:  Oher variables with the FIT_ prefix may be added to `fit`, so it is safer
        !          1832:  not to use that prefix for user-defined variables.
        !          1833:
        !          1834:  The variables FIT_SKIP and FIT_INDEX were used by earlier releases of
        !          1835:  `gnuplot` with a 'fit' patch called `gnufit` and are no longer available.
        !          1836:  The datafile `every` modifier provides the functionality of FIT_SKIP.
        !          1837:  FIT_INDEX was used for multi-branch fitting, but multi-branch fitting of
        !          1838:  one independent variable is now done as a pseudo-3D fit in which the
        !          1839:  second independent variable and `using` are used to specify the branch.
        !          1840:  See `fit multi-branch`.
        !          1841: 4 environment variables
        !          1842: ?commands fit_control environment
        !          1843: ?fit_control environment
        !          1844: ?fit control environment
        !          1845:  The environment variables must be defined before `gnuplot` is executed; how
        !          1846:  to do so depends on your operating system.
        !          1847:
        !          1848:        FIT_LOG
        !          1849:  changes the name (and/or path) of the file to which the fit log will be
        !          1850:  written from the default of "fit.log" in the working directory.
        !          1851:
        !          1852:        FIT_SCRIPT
        !          1853:  specifies a command that may be executed after an user interrupt. The default
        !          1854:  is `replot`, but a `plot` or `load` command may be useful to display a plot
        !          1855:  customized to highlight the progress of the fit.
        !          1856: 3 multi-branch
        !          1857: ?commands fit multi-branch
        !          1858: ?fit multi-branch
        !          1859: ?multi-branch
        !          1860: ?branch
        !          1861:  In multi-branch fitting, multiple data sets can be simultaneously fit with
        !          1862:  functions of one independent variable having common parameters by minimizing
        !          1863:  the total WSSR.  The function and parameters (branch) for each data set are
        !          1864:  selected by using a 'pseudo-variable', e.g., either the dataline number (a
        !          1865:  'column' index of -1) or the datafile index (-2), as the second independent
        !          1866:  variable.
        !          1867:
        !          1868:  Example:  Given two exponential decays of the form, z=f(x), each describing
        !          1869:  a different data set but having a common decay time, estimate the values of
        !          1870:  the parameters.  If the datafile has the format x:z:s, then
        !          1871:       f(x,y) = (y==0) ? a*exp(-x/tau) : b*exp(-x/tau)
        !          1872:       fit f(x,y) 'datafile' using  1:-1:2:3  via a, b, tau
        !          1873:
        !          1874:  For a more complicated example, see the file "hexa.fnc" used by the
        !          1875:  "fit.dem" demo.
        !          1876:
        !          1877:  Appropriate weighting may be required since unit weights may cause one
        !          1878:  branch to predominate if there is a difference in the scale of the dependent
        !          1879:  variable.  Fitting each branch separately, using the multi-branch solution
        !          1880:  as initial values, may give an indication as to the relative effect of each
        !          1881:  branch on the joint solution.
        !          1882: 3 starting values
        !          1883: ?commands fit starting_values
        !          1884: ?fit starting_values
        !          1885: ?starting_values
        !          1886:  Nonlinear fitting is not guaranteed to converge to the global optimum (the
        !          1887:  solution with the smallest sum of squared residuals, SSR), and can get stuck
        !          1888:  at a local minimum.  The routine has no way to determine that;  it is up to
        !          1889:  you to judge whether this has happened.
        !          1890:
        !          1891:  `fit` may, and often will get "lost" if started far from a solution, where
        !          1892:  SSR is large and changing slowly as the parameters are varied, or it may
        !          1893:  reach a numerically unstable region (e.g., too large a number causing a
        !          1894:  floating point overflow) which results in an "undefined value" message
        !          1895:  or `gnuplot` halting.
        !          1896:
        !          1897:  To improve the chances of finding the global optimum, you should set the
        !          1898:  starting values at least roughly in the vicinity of the solution, e.g.,
        !          1899:  within an order of magnitude, if possible.  The closer your starting values
        !          1900:  are to the solution, the less chance of stopping at another minimum.  One way
        !          1901:  to find starting values is to plot data and the fitting function on the same
        !          1902:  graph and change parameter values and `replot` until reasonable similarity
        !          1903:  is reached.  The same plot is also useful to check whether the fit stopped at
        !          1904:  a minimum with a poor fit.
        !          1905:
        !          1906:  Of course, a reasonably good fit is not proof there is not a "better" fit (in
        !          1907:  either a statistical sense, characterized by an improved goodness-of-fit
        !          1908:  criterion, or a physical sense, with a solution more consistent with the
        !          1909:  model.)  Depending on the problem, it may be desirable to `fit` with various
        !          1910:  sets of starting values, covering a reasonable range for each parameter.
        !          1911: 3 tips
        !          1912: ?commands fit tips
        !          1913: ?fit tips
        !          1914: ?tips
        !          1915:  Here are some tips to keep in mind to get the most out of `fit`.  They're not
        !          1916:  very organized, so you'll have to read them several times until their essence
        !          1917:  has sunk in.
        !          1918:
        !          1919:  The two forms of the `via` argument to `fit` serve two largely distinct
        !          1920:  purposes.  The `via "file"` form is best used for (possibly unattended) batch
        !          1921:  operation, where you just supply the startup values in a file and can later
        !          1922:  use `update` to copy the results back into another (or the same) parameter
        !          1923:  file.
        !          1924:
        !          1925:  The `via var1, var2, ...` form is best used interactively, where the command
        !          1926:  history mechanism may be used to edit the list of parameters to be fitted or
        !          1927:  to supply new startup values for the next try.  This is particularly useful
        !          1928:  for hard problems, where a direct fit to all parameters at once won't work
        !          1929:  without good starting values.  To find such, you can iterate several times,
        !          1930:  fitting only some of the parameters, until the values are close enough to the
        !          1931:  goal that the final fit to all parameters at once will work.
        !          1932:
        !          1933:  Make sure that there is no mutual dependency among parameters of the function
        !          1934:  you are fitting.  For example, don't try to fit a*exp(x+b), because
        !          1935:  a*exp(x+b)=a*exp(b)*exp(x).  Instead, fit either a*exp(x) or exp(x+b).
        !          1936:
        !          1937:  A technical issue:  the parameters must not be too different in magnitude.
        !          1938:  The larger the ratio of the largest and the smallest absolute parameter
        !          1939:  values, the slower the fit will converge.  If the ratio is close to or above
        !          1940:  the inverse of the machine floating point precision, it may take next to
        !          1941:  forever to converge, or refuse to converge at all.  You will have to adapt
        !          1942:  your function to avoid this, e.g., replace 'parameter' by '1e9*parameter' in
        !          1943:  the function definition, and divide the starting value by 1e9.
        !          1944:
        !          1945:  If you can write your function as a linear combination of simple functions
        !          1946:  weighted by the parameters to be fitted, by all means do so.  That helps a
        !          1947:  lot, because the problem is no longer nonlinear and should converge with only
        !          1948:  a small number of iterations, perhaps just one.
        !          1949:
        !          1950:  Some prescriptions for analysing data, given in practical experimentation
        !          1951:  courses, may have you first fit some functions to your data, perhaps in a
        !          1952:  multi-step process of accounting for several aspects of the underlying
        !          1953:  theory one by one, and then extract the information you really wanted from
        !          1954:  the fitting parameters of those functions.  With `fit`, this may often be
        !          1955:  done in one step by writing the model function directly in terms of the
        !          1956:  desired parameters.  Transforming data can also quite often be avoided,
        !          1957:  though sometimes at the cost of a more difficult fit problem.  If you think
        !          1958:  this contradicts the previous paragraph about simplifying the fit function,
        !          1959:  you are correct.
        !          1960:
        !          1961:  A "singular matrix" message indicates that this implementation of the
        !          1962:  Marquardt-Levenberg algorithm can't calculate parameter values for the next
        !          1963:  iteration.  Try different starting values, writing the function in another
        !          1964:  form, or a simpler function.
        !          1965:
        !          1966:  Finally, a nice quote from the manual of another fitting package (fudgit),
        !          1967:  that kind of summarizes all these issues:  "Nonlinear fitting is an art!"
        !          1968: 2 help
        !          1969: ?commands help
        !          1970: ?help
        !          1971:  The `help` command displays on-line help. To specify information on a
        !          1972:  particular topic use the syntax:
        !          1973:
        !          1974:        help {<topic>}
        !          1975:
        !          1976:  If <topic> is not specified, a short message is printed about `gnuplot`.
        !          1977:  After help for the requested topic is given, a menu of subtopics is given;
        !          1978:  help for a subtopic may be requested by typing its name, extending the help
        !          1979:  request.  After that subtopic has been printed, the request may be extended
        !          1980:  again or you may go back one level to the previous topic.  Eventually, the
        !          1981:  `gnuplot` command line will return.
        !          1982:
        !          1983:  If a question mark (?) is given as the topic, the list of topics currently
        !          1984:  available is printed on the screen.
        !          1985: 2 if
        !          1986: ?commands if
        !          1987: ?if
        !          1988:  The `if` command allows commands to be executed conditionally.
        !          1989:
        !          1990:  Syntax:
        !          1991:        if (<condition>) <command-line>
        !          1992:
        !          1993:  <condition> will be evaluated.  If it is true (non-zero), then the command(s)
        !          1994:  of the <command-line> will be executed.  If <condition> is false (zero), then
        !          1995:  the entire <command-line> is ignored.  Note that use of `;` to allow multiple
        !          1996:  commands on the same line will _not_ end the conditionalized commands.
        !          1997:
        !          1998:  Examples:
        !          1999:        pi=3
        !          2000:        if (pi!=acos(-1)) print "?Fixing pi!"; pi=acos(-1); print pi
        !          2001:  will display:
        !          2002:        ?Fixing pi!
        !          2003:        3.14159265358979
        !          2004:  but
        !          2005:        if (1==2) print "Never see this"; print "Or this either"
        !          2006:  will not display anything.
        !          2007:
        !          2008:  See `reread` for an example of how `if` and `reread` can be used together to
        !          2009:  perform a loop.
        !          2010: 2 load
        !          2011: ?commands load
        !          2012: ?load
        !          2013:  The `load` command executes each line of the specified input file as if it
        !          2014:  had been typed in interactively.  Files created by the `save` command can
        !          2015:  later be `load`ed.  Any text file containing valid commands can be created
        !          2016:  and then executed by the `load` command.  Files being `load`ed may themselves
        !          2017:  contain `load` or `call` commands.  See `comment` for information about
        !          2018:  comments in commands.  To `load` with arguments, see `call`.
        !          2019:
        !          2020:  The `load` command _must_ be the last command on a multi-command line.
        !          2021:
        !          2022:  Syntax:
        !          2023:        load "<input-file>"
        !          2024:
        !          2025:  The name of the input file must be enclosed in quotes.
        !          2026:
        !          2027:  The special filename "-" may be used to `load` commands from standard input.
        !          2028:  This allows a `gnuplot` command file to accept some commands from standard
        !          2029:  input.  Please see "help batch/interactive" for more details.
        !          2030:
        !          2031:  Examples:
        !          2032:        load 'work.gnu'
        !          2033:        load "func.dat"
        !          2034:
        !          2035:  The `load` command is performed implicitly on any file names given as
        !          2036:  arguments to `gnuplot`.  These are loaded in the order specified, and
        !          2037:  then `gnuplot` exits.
        !          2038: 2 pause
        !          2039: ?commands pause
        !          2040: ?pause
        !          2041:  The `pause` command displays any text associated with the command and then
        !          2042:  waits a specified amount of time or until the carriage return is pressed.
        !          2043:  `pause` is especially useful in conjunction with `load` files.
        !          2044:
        !          2045:  Syntax:
        !          2046:        pause <time> {"<string>"}
        !          2047:
        !          2048:  <time> may be any integer constant or expression.  Choosing -1 will wait
        !          2049:  until a carriage return is hit, zero (0) won't pause at all, and a positive
        !          2050:  integer will wait the specified number of seconds.  `pause 0` is synonymous
        !          2051:  with `print`.
        !          2052:
        !          2053:  Note: Since `pause` communicates with the operating system rather than the
        !          2054:  graphics, it may behave differently with different device drivers (depending
        !          2055:  upon how text and graphics are mixed).
        !          2056:
        !          2057:  Examples:
        !          2058:        pause -1    # Wait until a carriage return is hit
        !          2059:        pause 3     # Wait three seconds
        !          2060:        pause -1  "Hit return to continue"
        !          2061:        pause 10  "Isn't this pretty?  It's a cubic spline."
        !          2062:
        !          2063: 2 plot
        !          2064: ?commands plot
        !          2065: ?plot
        !          2066:  `plot` is the primary command for drawing plots with `gnuplot`.  It creates
        !          2067:  plots of functions and data in many, many ways.  `plot` is used to draw 2-d
        !          2068:  functions and data; `splot` draws 2-d projections of 3-d surfaces and data.
        !          2069:  `plot` and `splot` contain many common features; see `splot` for differences.
        !          2070:  Note specifically that `splot`'s `binary` and `matrix` options do not exist
        !          2071:  for `plot`.
        !          2072:
        !          2073:  Syntax:
        !          2074:        plot {<ranges>}
        !          2075:             {<function> | {"<datafile>" {datafile-modifiers}}}
        !          2076:             {axes <axes>} {<title-spec>} {with <style>}
        !          2077:             {, {definitions,} <function> ...}
        !          2078:
        !          2079:  where either a <function> or the name of a data file enclosed in quotes is
        !          2080:  supplied.  A function is a mathematical expression or a pair of mathematical
        !          2081:  expressions in parametric mode.  The expressions may be defined completely or
        !          2082:  in part earlier in the stream of `gnuplot` commands (see `user-defined`).
        !          2083:
        !          2084:  It is also possible to define functions and parameters on the `plot` command
        !          2085:  itself.  This is done merely by isolating them from other items with commas.
        !          2086:
        !          2087:  There are four possible sets of axes available; the keyword <axes> is used to
        !          2088:  select the axes for which a particular line should be scaled.  `x1y1` refers
        !          2089:  to the axes on the bottom and left; `x2y2` to those on the top and right;
        !          2090:  `x1y2` to those on the bottom and right; and `x2y1` to those on the top and
        !          2091:  left.  Ranges specified on the `plot` command apply only to the first set of
        !          2092:  axes (bottom left).
        !          2093:
        !          2094:  Examples:
        !          2095:        plot sin(x)
        !          2096:        plot f(x) = sin(x*a), a = .2, f(x), a = .4, f(x)
        !          2097:        plot [t=1:10] [-pi:pi*2] tan(t), \
        !          2098:             "data.1" using (tan($2)):($3/$4) smooth csplines \
        !          2099:                      axes x1y2 notitle with lines 5
        !          2100:
        !          2101: 3 data-file
        !          2102: ?commands plot datafile
        !          2103: ?plot datafile
        !          2104: ?data-file
        !          2105: ?datafile
        !          2106: ?data
        !          2107:  Discrete data contained in a file can be displayed by specifying the name of
        !          2108:  the data file (enclosed in single or double quotes) on the `plot` command line.
        !          2109:
        !          2110:  Syntax:
        !          2111:        plot '<file_name>' {index <index list>}
        !          2112:                              {every <every list>}
        !          2113:                              {thru <thru expression>}
        !          2114:                              {using <using list>}
        !          2115:                              {smooth <option>}
        !          2116:
        !          2117:  The modifiers `index`, `every`, `thru`, `using`, and `smooth` are discussed
        !          2118:  separately.  In brief, `index` selects which data sets in a multi-data-set
        !          2119:  file are to be plotted, `every` specifies which points within a single data
        !          2120:  set are to be plotted, `using` determines how the columns within a single
        !          2121:  record are to be interpreted (`thru` is a special case of `using`), and
        !          2122:  `smooth` allows for simple interpolation and approximation.  ('splot' has a
        !          2123:  similar syntax, but does not support the `smooth` and `thru` options.)
        !          2124:
        !          2125:  Data files should contain at least one data point per record (`using` can
        !          2126:  select one data point from the record).  Records beginning with `#` (and
        !          2127:  also with `!` on VMS) will be treated as comments and ignored.  Each data
        !          2128:  point represents an (x,y) pair.  For `plot`s with error bars (see `set style
        !          2129:  errorbars`), each data point is (x,y,ydelta), (x,y,ylow,yhigh), (x,y,xdelta),
        !          2130:  (x,y,xlow,xhigh), or (x,y,xlow,xhigh,ylow,yhigh).  In all cases, the numbers
        !          2131:  on each record of a data file must be separated by white space (one or more
        !          2132:  blanks or tabs), unless a format specifier is provided by the `using` option.
        !          2133:  This white space divides each record into columns.
        !          2134:
        !          2135:  Data may be written in exponential format with the exponent preceded by the
        !          2136:  letter e, E, d, D, q, or Q.
        !          2137:
        !          2138:  Only one column (the y value) need be provided.  If x is omitted, `gnuplot`
        !          2139:  provides integer values starting at 0.
        !          2140:
        !          2141:  In datafiles, blank records (records with no characters other than blanks and
        !          2142:  a newline and/or carriage return) are significant---pairs of blank records
        !          2143:  separate `index`es (see `plot datafile index`).  Data separated by double
        !          2144:  blank records are treated as if they were in separate data files.
        !          2145:
        !          2146:  Single blank records designate discontinuities in a `plot`; no line will join
        !          2147:  points separated by a blank records (if they are plotted with a line style).
        !          2148:
        !          2149:  If autoscaling has been enabled (`set autoscale`), the axes are automatically
        !          2150:  extended to include all datapoints, with a whole number of tic marks if tics
        !          2151:  are being drawn.  This has two consequences: i) For `splot`, the corner of
        !          2152:  the surface may not coincide with the corner of the base.  In this case, no
        !          2153:  vertical line is drawn.  ii) When plotting data with the same x range on a
        !          2154:  dual-axis graph, the x coordinates may not coincide if the x2tics are not
        !          2155:  being drawn.  This is because the x axis has been autoextended to a whole
        !          2156:  number of tics, but the x2 axis has not.  The following example illustrates
        !          2157:  the problem:
        !          2158:
        !          2159:        reset; plot '-', '-'
        !          2160:        1 1
        !          2161:        19 19
        !          2162:        e
        !          2163:        1 1
        !          2164:        19 19
        !          2165:        e
        !          2166: 4 every
        !          2167: ?commands plot datafile every
        !          2168: ?plot datafile every
        !          2169: ?plot every
        !          2170: ?data-file every
        !          2171: ?datafile every
        !          2172: ?every
        !          2173:  The `every` keyword allows a periodic sampling of a data set to be plotted.
        !          2174:
        !          2175:  In the discussion a "point" is a datum defined by a single record in the
        !          2176:  file; "block" here will mean the same thing as "datablock" (see `glossary`).
        !          2177:
        !          2178:  Syntax:
        !          2179:        plot 'file' every {<point_incr>}
        !          2180:                            {:{<block_incr>}
        !          2181:                              {:{<start_point>}
        !          2182:                                {:{<start_block>}
        !          2183:                                  {:{<end_point>}
        !          2184:                                    {:<end_block>}}}}}
        !          2185:
        !          2186:  The data points to be plotted are selected according to a loop from
        !          2187:  <`start_point`> to <`end_point`> with increment <`point_incr`> and the
        !          2188:  blocks according to a loop from <`start_block`> to <`end_block`> with
        !          2189:  increment <`block_incr`>.
        !          2190:
        !          2191:  The first datum in each block is numbered '0', as is the first block in the
        !          2192:  file.
        !          2193:
        !          2194:  Note that records containing unplottable information are counted.
        !          2195:
        !          2196:  Any of the numbers can be omitted; the increments default to unity, the start
        !          2197:  values to the first point or block, and the end values to the last point or
        !          2198:  block.  If `every` is not specified, all points in all lines are plotted.
        !          2199:
        !          2200:  Examples:
        !          2201:        every :::3::3    # selects just the fourth block ('0' is first)
        !          2202:        every :::::9     # selects the first 10 blocks
        !          2203:        every 2:2        # selects every other point in every other block
        !          2204:        every ::5::15    # selects points 5 through 15 in each block
        !          2205: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/simple/simple.html">Simple Plot Demos </a>,
        !          2206: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/surfacea/surfacea.html">Non-parametric splot demos </a>, and
        !          2207: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/surfaceb/surfaceb.html">Parametric splot demos.</a>
        !          2208: 4 example datafile
        !          2209: ?commands plot datafile example
        !          2210: ?plot datafile example
        !          2211: ?plot example
        !          2212: ?datafile example
        !          2213: ?data-file example
        !          2214: ?example
        !          2215:  This example plots the data in the file "population.dat" and a theoretical
        !          2216:  curve:
        !          2217:
        !          2218:        pop(x) = 103*exp((1965-x)/10)
        !          2219:        plot [1960:1990] 'population.dat', pop(x)
        !          2220:
        !          2221:  The file "population.dat" might contain:
        !          2222:
        !          2223:        # Gnu population in Antarctica since 1965
        !          2224:           1965   103
        !          2225:           1970   55
        !          2226:           1975   34
        !          2227:           1980   24
        !          2228:           1985   10
        !          2229:
        !          2230: ^ <img align=bottom src="http://www.nas.nasa.gov/~woo/gnuplot/doc/population.gif" alt="[population.gif]" width=640 height=480>
        !          2231: 4 index
        !          2232: ?commands plot datafile index
        !          2233: ?plot datafile index
        !          2234: ?plot index
        !          2235: ?data-file index
        !          2236: ?datafile index
        !          2237: ?index
        !          2238:  The `index` keyword allows only some of the data sets in a multi-data-set
        !          2239:  file to be plotted.
        !          2240:
        !          2241:  Syntax:
        !          2242:        plot 'file' index <m>{{:<n>}:<p>}
        !          2243:
        !          2244:  Data sets are separated by pairs of blank records.  `index <m>` selects only
        !          2245:  set <m>; `index <m>:<n>` selects sets in the range <m> to <n>; and `index
        !          2246:  <m>:<n>:<p>` selects indices <m>, <m>+<p>, <m>+2<p>, etc., but stopping at
        !          2247:  <n>.  Following C indexing, the index 0 is assigned to the first data set in
        !          2248:  the file.  Specifying too large an index results in an error message.  If
        !          2249:  `index` is not specified, all sets are plotted as a single data set.
        !          2250:
        !          2251:  Example:
        !          2252:        plot 'file' index 4:5
        !          2253: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/multimsh/multimsh.html"> splot with indices demo. </a>
        !          2254: 4 smooth
        !          2255: ?commands plot datafile smooth
        !          2256: ?plot datafile smooth
        !          2257: ?plot smooth
        !          2258: ?data-file smooth
        !          2259: ?datafile smooth
        !          2260: ?smooth
        !          2261:  `gnuplot` includes a few general-purpose routines for interpolation and
        !          2262:  approximation of data; these are grouped under the `smooth` option.  More
        !          2263:  sophisticated data processing may be performed by preprocessing the data
        !          2264:  externally or by using `fit` with an appropriate model.
        !          2265:
        !          2266:  Syntax:
        !          2267:        smooth {unique | csplines | acsplines | bezier | sbezier}
        !          2268:
        !          2269:  `unique` plots the data after making them monotonic.  Each of the other
        !          2270:  routines uses the data to determine the coefficients of a continuous curve
        !          2271:  between the endpoints of the data.  This curve is then plotted in the same
        !          2272:  manner as a function, that is, by finding its value at uniform intervals
        !          2273:  along the abscissa (see `set samples`) and connecting these points with
        !          2274:  straight line segments (if a line style is chosen).
        !          2275:
        !          2276:  If `autoscale` is in effect, the ranges will be computed such that the
        !          2277:  plotted curve lies within the borders of the graph.
        !          2278:
        !          2279:  If too few points are available to allow the selected option to be applied,
        !          2280:  an error message is produced.  The minimum number is one for `unique`, four
        !          2281:  for `acsplines`, and three for the others.
        !          2282:
        !          2283:  The `smooth` options have no effect on function plots.
        !          2284: 5 acsplines
        !          2285: ?commands plot datafile smooth acsplines
        !          2286: ?plot datafile smooth acsplines
        !          2287: ?data-file smooth acsplines
        !          2288: ?datafile smooth acsplines
        !          2289: ?plot smooth acsplines
        !          2290: ?plot acsplines
        !          2291: ?smooth acsplines
        !          2292: ?acsplines
        !          2293:  The `acsplines` option approximates the data with a "natural smoothing spline".
        !          2294:  After the data are made monotonic in x (see `smooth unique`), a curve is
        !          2295:  piecewise constructed from segments of cubic polynomials whose coefficients
        !          2296:  are found by the weighting the data points; the weights are taken from the
        !          2297:  third column in the data file.  That default can be modified by the third
        !          2298:  entry in the `using` list, e.g.,
        !          2299:        plot 'data-file' using 1:2:(1.0) smooth acsplines
        !          2300:
        !          2301:  Qualitatively, the absolute magnitude of the weights determines the number
        !          2302:  of segments used to construct the curve.  If the weights are large, the
        !          2303:  effect of each datum is large and the curve approaches that produced by
        !          2304:  connecting consecutive points with natural cubic splines.  If the weights are
        !          2305:  small, the curve is composed of fewer segments and thus is smoother; the
        !          2306:  limiting case is the single segment produced by a weighted linear least
        !          2307:  squares fit to all the data.  The smoothing weight can be expressed in terms
        !          2308:  of errors as a statistical weight for a point divided by a "smoothing factor"
        !          2309:  for the curve so that (standard) errors in the file can be used as smoothing
        !          2310:  weights.
        !          2311:
        !          2312:  Example:
        !          2313:        sw(x,S)=1/(x*x*S)
        !          2314:        plot 'data_file' using 1:2:(sw($3,100)) smooth acsplines
        !          2315: 5 bezier
        !          2316: ?commands plot datafile smooth bezier
        !          2317: ?plot datafile smooth bezier
        !          2318: ?plot smooth bezier
        !          2319: ?data-file smooth bezier
        !          2320: ?datafile smooth bezier
        !          2321: ?plot bezier
        !          2322: ?smooth bezier
        !          2323: ?bezier
        !          2324:  The `bezier` option approximates the data with a Bezier curve of degree n
        !          2325:  (the number of data points) that connects the endpoints.
        !          2326: 5 csplines
        !          2327: ?commands plot datafile smooth csplines
        !          2328: ?plot datafile smooth csplines
        !          2329: ?plot smooth csplines
        !          2330: ?data-file smooth csplines
        !          2331: ?datafile smooth csplines
        !          2332: ?plot csplines
        !          2333: ?smooth csplines
        !          2334: ?csplines
        !          2335:  The `csplines` option connects consecutive points by natural cubic splines
        !          2336:  after rendering the data monotonic (see `smooth unique`).
        !          2337: 5 sbezier
        !          2338: ?commands plot datafile smooth sbezier
        !          2339: ?plot datafile smooth sbezier
        !          2340: ?plot smooth sbezier
        !          2341: ?data-file smooth sbezier
        !          2342: ?datafile smooth sbezier
        !          2343: ?plot sbezier
        !          2344: ?smooth sbezier
        !          2345: ?sbezier
        !          2346:  The `sbezier` option first renders the data monotonic (`unique`) and then
        !          2347:  applies the `bezier` algorithm.
        !          2348: 5 unique
        !          2349: ?commands plot datafile smooth unique
        !          2350: ?plot datafile smooth unique
        !          2351: ?plot smooth unique
        !          2352: ?data-file smooth unique
        !          2353: ?datafile smooth unique
        !          2354: ?plot unique
        !          2355: ?smooth unique
        !          2356: ?unique
        !          2357:  The `unique` option makes the data monotonic in x; points with the same
        !          2358:  x-value are replaced by a single point having the average y-value.  The
        !          2359:  resulting points are then connected by straight line segments.
        !          2360: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/mgr/mgr.html"> See demos. </a>
        !          2361: 4 special-filenames
        !          2362: ?commands plot datafile special-filenames
        !          2363: ?plot datafile special-filenames
        !          2364: ?plot special-filenames
        !          2365: ?datafile special-filenames
        !          2366: ?special-filenames
        !          2367:  A special filename of `'-'` specifies that the data are inline; i.e., they
        !          2368:  follow the command.  Only the data follow the command; `plot` options like
        !          2369:  filters, titles, and line styles remain on the 'plot' command line.  This is
        !          2370:  similar to << in unix shell script, and $DECK in VMS DCL.  The data are
        !          2371:  entered as though they are being read from a file, one data point per record.
        !          2372:  The letter "e" at the start of the first column terminates data entry.  The
        !          2373:  `using` option can be applied to these data---using it to filter them through
        !          2374:  a function might make sense, but selecting columns probably doesn't!
        !          2375:
        !          2376:  `'-'` is intended for situations where it is useful to have data and commands
        !          2377:  together, e.g., when `gnuplot` is run as a sub-process of some front-end
        !          2378:  application.  Some of the demos, for example, might use this feature.  While
        !          2379:  `plot` options such as `index` and `every` are recognized, their use forces
        !          2380:  you to enter data that won't be used.  For example, while
        !          2381:
        !          2382:        plot '-' index 0, '-' index 1
        !          2383:        2
        !          2384:        4
        !          2385:        6
        !          2386:
        !          2387:
        !          2388:        10
        !          2389:        12
        !          2390:        14
        !          2391:        e
        !          2392:        2
        !          2393:        4
        !          2394:        6
        !          2395:
        !          2396:
        !          2397:        10
        !          2398:        12
        !          2399:        14
        !          2400:        e
        !          2401:
        !          2402:  does indeed work,
        !          2403:
        !          2404:        plot '-', '-'
        !          2405:        2
        !          2406:        4
        !          2407:        6
        !          2408:        e
        !          2409:        10
        !          2410:        12
        !          2411:        14
        !          2412:        e
        !          2413:
        !          2414:  is a lot easier to type.
        !          2415:
        !          2416:  If you use `'-'` with `replot`, you may need to enter the data more than once
        !          2417:  (see `replot`).
        !          2418:
        !          2419:  A blank filename ('') specifies that the previous filename should be reused.
        !          2420:  This can be useful with things like
        !          2421:
        !          2422:        plot 'a/very/long/filename' using 1:2, '' using 1:3, '' using 1:4
        !          2423:
        !          2424:  (If you use both `'-'` and `''` on the same `plot` command, you'll need to
        !          2425:  have two sets of inline data, as in the example above.)
        !          2426:
        !          2427:  On some computer systems with a popen function (Unix), the datafile can be
        !          2428:  piped through a shell command by starting the file name with a '<'.  For
        !          2429:  example,
        !          2430:
        !          2431:        pop(x) = 103*exp(-x/10)
        !          2432:        plot "< awk '{print $1-1965, $2}' population.dat", pop(x)
        !          2433:
        !          2434:  would plot the same information as the first population example but with
        !          2435:  years since 1965 as the x axis.  If you want to execute this example, you
        !          2436:  have to delete all comments from the data file above or substitute the
        !          2437:  following command for the first part of the command above (the part up to
        !          2438:  the comma):
        !          2439:
        !          2440:        plot "< awk '$0 !~ /^#/ {print $1-1965, $2}' population.dat"
        !          2441:
        !          2442:  While this approach is most flexible, it is possible to achieve simple
        !          2443:  filtering with the `using` or `thru` keywords.
        !          2444: 4 thru
        !          2445: ?commands plot datafile thru
        !          2446: ?plot datafile thru
        !          2447: ?plot thru
        !          2448: ?data-file thru
        !          2449: ?datafile thru
        !          2450: ?thru
        !          2451:  The `thru` function is provided for backward compatibility.
        !          2452:
        !          2453:  Syntax:
        !          2454:        plot 'file' thru f(x)
        !          2455:
        !          2456:  It is equivalent to:
        !          2457:
        !          2458:        plot 'file' using 1:(f($2))
        !          2459:
        !          2460:  While the latter appears more complex, it is much more flexible.  The more
        !          2461:  natural
        !          2462:
        !          2463:        plot 'file' thru f(y)
        !          2464:
        !          2465:  also works (i.e. you can use y as the dummy variable).
        !          2466:
        !          2467:  `thru` is parsed for `splot` and `fit` but has no effect.
        !          2468: 4 using
        !          2469: ?commands plot datafile using
        !          2470: ?plot datafile using
        !          2471: ?plot using
        !          2472: ?data-file using
        !          2473: ?datafile using
        !          2474: ?using
        !          2475:  The most common datafile modifier is `using`.
        !          2476:
        !          2477:  Syntax:
        !          2478:        plot 'file' using {<entry> {:<entry> {:<entry> ...}}} {'format'}
        !          2479:
        !          2480:  If a format is specified, each datafile record is read using the C library's
        !          2481:  'scanf' function, with the specified format string.  Otherwise the record is
        !          2482:  read and broken into columns at spaces or tabs.  A format cannot be specified
        !          2483:  if time-format data is being used (this must be done by `set data time`).
        !          2484:
        !          2485:  The resulting array of data is then sorted into columns according to the
        !          2486:  entries.  Each <entry> may be a simple column number, which selects the
        !          2487:  datum, an expression enclosed in parentheses, or empty.  The expression can
        !          2488:  use $1 to access the first item read, $2 for the second item, and so on.  It
        !          2489:  can also use `column(x)` and `valid(x)` where x is an arbitrary expression
        !          2490:  resulting in an integer.  `column(x)` returns the x'th datum; `valid(x)`
        !          2491:  tests that the datum in the x'th column is a valid number.  A column number
        !          2492:  of 0 generates a number increasing (from zero) with each point, and is reset
        !          2493:  upon encountering two blank records.  A column number of -1 gives the
        !          2494:  dataline number, which starts at 0, increments at single blank records, and
        !          2495:  is reset at double blank records.  A column number of -2 gives the index
        !          2496:  number, which is incremented only when two blank records are found.  An empty
        !          2497:  <entry> will default to its order in the list of entries.  For example,
        !          2498:  `using ::4` is interpreted as `using 1:2:4`.
        !          2499:
        !          2500:  N.B.---the `call` command also uses $'s as a special character.  See `call`
        !          2501:  for details about how to include a column number in a `call` argument list.
        !          2502:
        !          2503:  If the `using` list has but a single entry, that <entry> will be used for y
        !          2504:  and the data point number is used for x; for example, "`plot 'file' using 1`"
        !          2505:  is identical to "`plot 'file' using 0:1`".  If the `using` list has two
        !          2506:  entries, these will be used for x and y.  Additional entries are usually
        !          2507:  errors in x and/or y.  See `set style` for details about plotting styles that
        !          2508:  make use of error information, and `fit` for use of error information in
        !          2509:  curve fitting.
        !          2510:
        !          2511:  'scanf' accepts several numerical specifications but `gnuplot` requires all
        !          2512:  inputs to be double-precision floating-point variables, so `lf` is the only
        !          2513:  permissible specifier.  'scanf' expects to see white space---a blank, tab
        !          2514:  ("\t"), newline ("\n"), or formfeed ("\f")---between numbers; anything else
        !          2515:  in the input stream must be explicitly skipped.
        !          2516:
        !          2517:  Note that the use of "\t", "\n", or "\f" or requires use of double-quotes
        !          2518:  rather than single-quotes.
        !          2519:
        !          2520:  Examples:
        !          2521:
        !          2522:  This creates a plot of the sum of the 2nd and 3rd data against the first:
        !          2523:  (The format string specifies comma- rather than space-separated columns.)
        !          2524:        plot 'file' using 1:($2+$3) '%lf,%lf,%lf'
        !          2525:
        !          2526:  In this example the data are read from the file "MyData" using a more
        !          2527:  complicated format:
        !          2528:        plot 'MyData' using "%*lf%lf%*20[^\n]%lf"
        !          2529:
        !          2530:  The meaning of this format is:
        !          2531:
        !          2532:        %*lf        ignore a number
        !          2533:        %lf         read a double-precision number (x by default)
        !          2534:        %*20[^\n]   ignore 20 non-newline characters
        !          2535:        %lf         read a double-precision number (y by default)
        !          2536:
        !          2537:  One trick is to use the ternary `?:` operator to filter data:
        !          2538:
        !          2539:        plot 'file' using 1:($3>10 ? $2 : 1/0)
        !          2540:
        !          2541:  which plots the datum in column two against that in column one provided
        !          2542:  the datum in column three exceeds ten.  `1/0` is undefined; `gnuplot`
        !          2543:  quietly ignores undefined points, so unsuitable points are suppressed.
        !          2544:
        !          2545:  In fact, you can use a constant expression for the column number, provided it
        !          2546:  doesn't start with an opening parenthesis; constructs like `using
        !          2547:  0+(complicated expression)` can be used.  The crucial point is that the
        !          2548:  expression is evaluated once if it doesn't start with a left parenthesis, or
        !          2549:  once for each data point read if it does.
        !          2550:
        !          2551:  If timeseries data are being used, the time can span multiple columns.  The
        !          2552:  starting column should be specified.  Note that the spaces within the time
        !          2553:  must be included when calculating starting columns for other data.  E.g., if
        !          2554:  the first element on a line is a time with an embedded space, the y value
        !          2555:  should be specified as column three.
        !          2556:
        !          2557:  It should be noted that `plot 'file'`, `plot 'file' using 1:2`, and `plot
        !          2558:  'file' using ($1):($2)` can be subtly different: 1) if `file` has some lines
        !          2559:  with one column and some with two, the first will invent x values when they
        !          2560:  are missing, the second will quietly ignore the lines with one column, and
        !          2561:  the third will store an undefined value for lines with one point (so that in
        !          2562:  a plot with lines, no line joins points across the bad point); 2) if a line
        !          2563:  contains text at the first column, the first will abort the plot on an error,
        !          2564:  but the second and third should quietly skip the garbage.
        !          2565:
        !          2566:  In fact, it is often possible to plot a file with lots of lines of garbage at
        !          2567:  the top simply by specifying
        !          2568:
        !          2569:        plot 'file' using 1:2
        !          2570:
        !          2571:  However, if you want to leave text in your data files, it is safer to put the
        !          2572:  comment character (#) in the first column of the text lines.
        !          2573: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/using/using.html"> Feeble using demos. </a>
        !          2574: 3 errorbars
        !          2575: ?commands plot errorbars
        !          2576: ?commands splot errorbars
        !          2577: ?plot errorbars
        !          2578: ?splot errorbars
        !          2579: ?errorbars
        !          2580:  Error bars are supported for 2-d data file plots by reading one to four
        !          2581:  additional columns (or `using` entries); these additional values are used in
        !          2582:  different ways by the various errorbar styles.
        !          2583:
        !          2584:  In the default situation, `gnuplot` expects to see three, four, or six
        !          2585:  numbers on each line of the data file---either
        !          2586:
        !          2587:        (x, y, ydelta),
        !          2588:        (x, y, ylow, yhigh),
        !          2589:        (x, y, xdelta),
        !          2590:        (x, y, xlow, xhigh),
        !          2591:        (x, y, xdelta, ydelta), or
        !          2592:        (x, y, xlow, xhigh, ylow, yhigh).
        !          2593:
        !          2594:  The x coordinate must be specified.  The order of the numbers must be
        !          2595:  exactly as given above, though the `using` qualifier can manipulate the order
        !          2596:  and provide values for missing columns.  For example,
        !          2597:
        !          2598:        plot 'file' with errorbars
        !          2599:        plot 'file' using 1:2:(sqrt($1)) with xerrorbars
        !          2600:        plot 'file' using 1:2:($1-$3):($1+$3):4:5 with xyerrorbars
        !          2601:
        !          2602:  The last example is for a file containing an unsupported combination of
        !          2603:  relative x and absolute y errors.  The `using` entry generates absolute x min
        !          2604:  and max from the relative error.
        !          2605:
        !          2606:  The y error bar is a vertical line plotted from (x, ylow) to (x, yhigh).
        !          2607:  If ydelta is specified instead of ylow and yhigh, ylow = y - ydelta and
        !          2608:  yhigh = y + ydelta are derived.  If there are only two numbers on the record,
        !          2609:  yhigh and ylow are both set to y.  The x error bar is a horizontal line
        !          2610:  computed in the same fashion.  To get lines plotted between the data points,
        !          2611:  `plot` the data file twice, once with errorbars and once with lines (but
        !          2612:  remember to use the `notitle` option on one to avoid two entries in the key).
        !          2613:
        !          2614:  The error bars have crossbars at each end unless `set bar` is used (see `set
        !          2615:  bar` for details).
        !          2616:
        !          2617:  If autoscaling is on, the ranges will be adjusted to include the error bars.
        !          2618: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/errorbar/errorbar.html"> Errorbar demos. </a>
        !          2619:
        !          2620:  See `plot using`, `plot with`, and `set style` for more information.
        !          2621: 3 parametric
        !          2622: ?commands plot parametric
        !          2623: ?commands splot parametric
        !          2624: ?plot parametric
        !          2625: ?splot parametric
        !          2626: ?parametric
        !          2627:  When in parametric mode (`set parametric`) mathematical expressions must be
        !          2628:  given in pairs for `plot` and in triplets for `splot`.
        !          2629:
        !          2630:  Examples:
        !          2631:        plot sin(t),t**2
        !          2632:        splot cos(u)*cos(v),cos(u)*sin(v),sin(u)
        !          2633:
        !          2634:  Data files are plotted as before, except any preceding parametric function
        !          2635:  must be fully specified before a data file is given as a plot.  In other
        !          2636:  words, the x parametric function (`sin(t)` above) and the y parametric
        !          2637:  function (`t**2` above) must not be interrupted with any modifiers or data
        !          2638:  functions; doing so will generate a syntax error stating that the parametric
        !          2639:  function is not fully specified.
        !          2640:
        !          2641:  Other modifiers, such as `with` and `title`, may be specified only after the
        !          2642:  parametric function has been completed:
        !          2643:
        !          2644:        plot sin(t),t**2 title 'Parametric example' with linespoints
        !          2645: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/param/param.html"> Parametric Mode Demos. </a>
        !          2646: 3 ranges
        !          2647: ?commands plot ranges
        !          2648: ?commands splot ranges
        !          2649: ?plot ranges
        !          2650: ?splot ranges
        !          2651: ?ranges
        !          2652:  The optional ranges specify the region of the graph that will be displayed.
        !          2653:
        !          2654:  Syntax:
        !          2655:        [{<dummy-var>=}{{<min>}:{<max>}}]
        !          2656:        [{{<min>}:{<max>}}]
        !          2657:
        !          2658:  The first form applies to the independent variable (`xrange` or `trange`, if
        !          2659:  in parametric mode).  The second form applies to the dependent variable
        !          2660:  `yrange` (and `xrange`, too, if in parametric mode).  <dummy-var> is a new
        !          2661:  name for the independent variable.  (The defaults may be changed with `set
        !          2662:  dummy`.)  The optional <min> and <max> terms can be constant expressions or *.
        !          2663:
        !          2664:  In non-parametric mode, the order in which ranges must be given is `xrange`
        !          2665:  and `yrange`.
        !          2666:
        !          2667:  In parametric mode, the order for the `plot` command is `trange`, `xrange`,
        !          2668:  and `yrange`.  The following `plot` command shows setting the `trange` to
        !          2669:  [-pi:pi], the `xrange` to [-1.3:1.3] and the `yrange` to [-1:1] for the
        !          2670:  duration of the graph:
        !          2671:
        !          2672:        plot [-pi:pi] [-1.3:1.3] [-1:1] sin(t),t**2
        !          2673:
        !          2674:  Note that the x2range and y2range cannot be specified here---`set x2range`
        !          2675:  and `set y2range` must be used.
        !          2676:
        !          2677:  Ranges are interpreted in the order listed above for the appropriate mode.
        !          2678:  Once all those needed are specified, no further ones must be listed, but
        !          2679:  unneeded ones cannot be skipped---use an empty range `[]` as a placeholder.
        !          2680:
        !          2681:  `*` can be used to allow autoscaling of either of min and max.  See also
        !          2682:  `set autoscale`.
        !          2683:
        !          2684:  Ranges specified on the `plot` or `splot` command line affect only that
        !          2685:  graph; use the `set xrange`, `set yrange`, etc., commands to change the
        !          2686:  default ranges for future graphs.
        !          2687:
        !          2688:  With time data, you must provide the range (in the same manner as the time
        !          2689:  appears in the datafile) within quotes.  `gnuplot` uses the `timefmt` string
        !          2690:  to read the value---see `set timefmt`.
        !          2691:
        !          2692:  Examples:
        !          2693:
        !          2694:  This uses the current ranges:
        !          2695:        plot cos(x)
        !          2696:
        !          2697:  This sets the x range only:
        !          2698:        plot [-10:30] sin(pi*x)/(pi*x)
        !          2699:
        !          2700:  This is the same, but uses t as the dummy-variable:
        !          2701:        plot [t = -10 :30]  sin(pi*t)/(pi*t)
        !          2702:
        !          2703:  This sets both the x and y ranges:
        !          2704:        plot [-pi:pi] [-3:3]  tan(x), 1/x
        !          2705:
        !          2706:  This sets only the y range, and turns off autoscaling on both axes:
        !          2707:        plot [ ] [-2:sin(5)*-8] sin(x)**besj0(x)
        !          2708:
        !          2709:  This sets xmax and ymin only:
        !          2710:        plot [:200] [-pi:]  exp(sin(x))
        !          2711:
        !          2712:  This sets the x range for a timeseries:
        !          2713:        set timefmt "%d/%m/%y %H:%M"
        !          2714:        plot ["1/6/93 12:00":"5/6/93 12:00"] 'timedata.dat'
        !          2715:
        !          2716: ^<a href="http://www.nas.nasa.gov/~woo/gnuplot/ranges/ranges.html"> See Demo. </a>
        !          2717: 3 title
        !          2718: ?commands plot title
        !          2719: ?commands splot title
        !          2720: ?plot title
        !          2721: ?splot title
        !          2722:  A line title for each function and data set appears in the key, accompanied
        !          2723:  by a sample of the line and/or symbol used to represent it.  It can be
        !          2724:  changed by using the `title` option.
        !          2725:
        !          2726:  Syntax:
        !          2727:        title "<title>" | notitle
        !          2728:
        !          2729:  where <title> is the new title of the line and must be enclosed in quotes.
        !          2730:  The quotes will not be shown in the key.  A special character may be given as
        !          2731:  a backslash followed by its octal value ("\345").  The tab character "\t" is
        !          2732:  understood.  Note that backslash processing occurs only for strings enclosed
        !          2733:  in double quotes---use single quotes to prevent such processing.  The newline
        !          2734:  character "\n" is not processed in key entries in either type of string.
        !          2735:
        !          2736:  The line title and sample can be omitted from the key by using the keyword
        !          2737:  `notitle`.  A null title (`title ''`) is equivalent to `notitle`.  If only
        !          2738:  the sample is wanted, use one or more blanks (`title ' '`).
        !          2739:
        !          2740:  By default the line title is the function or file name as it appears on the
        !          2741:  `plot` command.  If it is a file name, any datafile modifiers specified will
        !          2742:  be included in the default title.
        !          2743:
        !          2744:  The layout of the key itself (position, title justification, etc.) can be
        !          2745:  controlled by `set key`.  Please see `set key` for details.
        !          2746:
        !          2747:  Examples:
        !          2748:
        !          2749:  This plots y=x with the title 'x':
        !          2750:        plot x
        !          2751:
        !          2752:  This plots x squared with title "x^2" and file "data.1" with title
        !          2753:  "measured data":
        !          2754:        plot x**2 title "x^2", 'data.1' t "measured data"
        !          2755:
        !          2756:  This puts an untitled circular border around a polar graph:
        !          2757:        set polar; plot my_function(t), 1 notitle
        !          2758: 3 with
        !          2759: ?commands plot with
        !          2760: ?commands splot with
        !          2761: ?commands plot style
        !          2762: ?commands splot style
        !          2763: ?plot with
        !          2764: ?plot style
        !          2765: ?splot with
        !          2766: ?splot style
        !          2767: ?style
        !          2768: ?with
        !          2769:  Functions and data may be displayed in one of a large number of styles.
        !          2770:  The `with` keyword provides the means of selection.
        !          2771:
        !          2772:  Syntax:
        !          2773:        with <style> { {linestyle | ls <line_style>}
        !          2774:                       | {{linetype | lt <line_type>}
        !          2775:                          {linewidth | lw <line_width>}
        !          2776:                          {pointtype | pt <point_type>}
        !          2777:                          {pointsize | ps <point_size>}} }
        !          2778:
        !          2779:  where <style> is either `lines`, `points`, `linespoints`, `impulses`, `dots`,
        !          2780:  `steps`, `fsteps`, `histeps`, `errorbars`, `xerrorbars`, `yerrorbars`,
        !          2781:  `xyerrorbars`, `boxes`, `boxerrorbars`, `boxxyerrorbars`, `financebars`,
        !          2782:  `candlesticks` or `vector`.  Some of these styles require additional
        !          2783:  information.  See `set style <style>` for details of each style.
        !          2784:
        !          2785:  Default styles are chosen with the `set function style` and `set data style`
        !          2786:  commands.
        !          2787:
        !          2788:  By default, each function and data file will use a different line type and
        !          2789:  point type, up to the maximum number of available types.  All terminal
        !          2790:  drivers support at least six different point types, and re-use them, in
        !          2791:  order, if more are required.  The LaTeX driver supplies an additional six
        !          2792:  point types (all variants of a circle), and thus will only repeat after 12
        !          2793:  curves are plotted with points.  The PostScript drivers (`postscript`)
        !          2794:  supplies a total of 64.
        !          2795:
        !          2796:  If you wish to choose the line or point type for a single plot, <line_type>
        !          2797:  and <point_type> may be specified.  These are positive integer constants (or
        !          2798:  expressions) that specify the line type and point type to be used for the
        !          2799:  plot.  Use `test` to display the types available for your terminal.
        !          2800:
        !          2801:  You may also scale the line width and point size for a plot by using
        !          2802:  <line_width> and <point_size>, which are specified relative to the default
        !          2803:  values for each terminal.  The pointsize may also be altered globally---see
        !          2804:  `set pointsize` for details.  But note that both <point_size> as set here and
        !          2805:  as set by `set pointsize` multiply the default point size---their effects are
        !          2806:  not cumulative.  That is, `set pointsize 2; plot x w p ps 3` will use points
        !          2807:  three times default size, not six.
        !          2808:
        !          2809:  If you have defined specific line type/width and point type/size combinations
        !          2810:  with `set linestyle`, one of these may be selected by setting <line_style> to
        !          2811:  the index of the desired style.
        !          2812:
        !          2813:  The keywords may be abbreviated as indicated.
        !          2814:
        !          2815:  Note that the `linewidth` and `pointsize` options are not supported by all
        !          2816:  terminals.
        !          2817:
        !          2818:  Examples:
        !          2819:
        !          2820:  This plots sin(x) with impulses:
        !          2821:        plot sin(x) with impulses
        !          2822:
        !          2823:  This plots x with points, x**2 with the default:
        !          2824:        plot x*y w points, x**2 + y**2
        !          2825:
        !          2826:  This plots tan(x) with the default function style, file "data.1" with lines:
        !          2827:        plot [ ] [-2:5] tan(x), 'data.1' with l
        !          2828:
        !          2829:  This plots "leastsq.dat" with impulses:
        !          2830:        plot 'leastsq.dat' w i
        !          2831:
        !          2832:  This plots the data file "population" with boxes:
        !          2833:        plot 'population' with boxes
        !          2834:
        !          2835:  This plots "exper.dat" with errorbars and lines connecting the points
        !          2836:  (errorbars require three or four columns):
        !          2837:        plot 'exper.dat' w lines, 'exper.dat' notitle w errorbars
        !          2838:
        !          2839:  This plots sin(x) and cos(x) with linespoints, using the same line type but
        !          2840:  different point types:
        !          2841:        plot sin(x) with linesp lt 1 pt 3, cos(x) with linesp lt 1 pt 4
        !          2842:
        !          2843:  This plots file "data" with points of type 3 and twice usual size:
        !          2844:        plot 'data' with points pointtype 3 pointsize 2
        !          2845:
        !          2846:  This plots two data sets with lines differing only by weight:
        !          2847:        plot 'd1' t "good" w l lt 2 lw 3, 'd2' t "bad" w l lt 2 lw 1
        !          2848:
        !          2849:  See `set style` to change the default styles.
        !          2850: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/styles/styles.html"> Styles demos. </a>
        !          2851: 2 print
        !          2852: ?commands print
        !          2853: ?print
        !          2854:  The `print` command prints the value of <expression> to the screen.  It is
        !          2855:  synonymous with `pause 0`.  <expression> may be anything that `gnuplot` can
        !          2856:  evaluate that produces a number, or it can be a string.
        !          2857:
        !          2858:  Syntax:
        !          2859:        print <expression> {, <expression>, ...}
        !          2860:
        !          2861:  See `expressions`.
        !          2862: 2 pwd
        !          2863: ?commands pwd
        !          2864: ?pwd
        !          2865:  The `pwd` command prints the name of the working directory to the screen.
        !          2866: 2 quit
        !          2867: ?commands quit
        !          2868: ?quit
        !          2869:  The `exit` and `quit` commands and END-OF-FILE character will exit `gnuplot`.
        !          2870:  Each of these commands will clear the output device (as does the `clear`
        !          2871:  command) before exiting.
        !          2872: 2 replot
        !          2873: ?commands replot
        !          2874: ?replot
        !          2875:  The `replot` command without arguments repeats the last `plot` or `splot`
        !          2876:  command.  This can be useful for viewing a plot with different `set` options,
        !          2877:  or when generating the same plot for several devices.
        !          2878:
        !          2879:  Arguments specified after a `replot` command will be added onto the last
        !          2880:  `plot` or `splot` command (with an implied ',' separator) before it is
        !          2881:  repeated.  `replot` accepts the same arguments as the `plot` and `splot`
        !          2882:  commands except that ranges cannot be specified.  Thus you can use `replot`
        !          2883:  to plot a function against the second axes if the previous command was `plot`
        !          2884:  but not if it was `splot`, and similarly you can use `replot` to add a plot
        !          2885:  from a binary file only if the previous command was `splot`.
        !          2886:
        !          2887:  N.B.---use of
        !          2888:
        !          2889:        plot '-' ; ... ; replot
        !          2890:
        !          2891:  is not recommended.  `gnuplot` does not store the inline data internally, so
        !          2892:  since `replot` appends new information to the previous `plot` and then
        !          2893:  executes the modified command, the `'-'` from the initial `plot` will expect
        !          2894:  to read inline data again.
        !          2895:
        !          2896:  Note that `replot` does not work in `multiplot` mode, since it reproduces
        !          2897:  only the last plot rather than the entire screen.
        !          2898:
        !          2899:  See also `command-line-editing` for ways to edit the last `plot` (`splot`)
        !          2900:  command.
        !          2901: 2 reread
        !          2902: ?commands reread
        !          2903: ?reread
        !          2904:  The `reread` command causes the current `gnuplot` command file, as specified
        !          2905:  by a `load` command or on the command line, to be reset to its starting
        !          2906:  point before further commands are read from it.  This essentially implements
        !          2907:  an endless loop of the commands from the beginning of the command file to
        !          2908:  the `reread` command.  (But this is not necessarily a disaster---`reread` can
        !          2909:  be very useful when used in conjunction with `if`.  See `if` for details.)
        !          2910:  The `reread` command has no effect if input from standard input.
        !          2911:
        !          2912:  Examples:
        !          2913:
        !          2914:  Suppose the file "looper" contains the commands
        !          2915:        a=a+1
        !          2916:        plot sin(x*a)
        !          2917:        pause -1
        !          2918:        if(a<5) reread
        !          2919:  and from within `gnuplot` you submit the commands
        !          2920:        a=0
        !          2921:        load 'looper'
        !          2922:  The result will be four plots (separated by the `pause` message).
        !          2923:
        !          2924:  Suppose the file "data" contains six columns of numbers with a total yrange
        !          2925:  from 0 to 10; the first is x and the next are five different functions of x.
        !          2926:  Suppose also that the file "plotter" contains the commands
        !          2927:        c_p = c_p+1
        !          2928:        plot "$0" using 1:c_p with lines linetype c_p
        !          2929:        if(c_p <  n_p) reread
        !          2930:  and from within `gnuplot` you submit the commands
        !          2931:        n_p=6
        !          2932:        c_p=1
        !          2933:        set nokey
        !          2934:        set yrange [0:10]
        !          2935:        set multiplot
        !          2936:        call 'plotter' 'data'
        !          2937:        set nomultiplot
        !          2938:  The result is a single graph consisting of five plots.  The yrange must be
        !          2939:  set explicitly to guarantee that the five separate graphs (drawn on top of
        !          2940:  each other in multiplot mode) will have exactly the same axes.  The linetype
        !          2941:  must be specified; otherwise all the plots would be drawn with the same type.
        !          2942: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/animate/animate.html"> Reread Animation Demo</a>
        !          2943: 2 reset
        !          2944: ?commands reset
        !          2945: ?reset
        !          2946:  The `reset` command causes all options that can be set with the `set`
        !          2947:  command to take on their default values.  The only exceptions are that the
        !          2948:  terminal set with `set term` and the output file set with `set output` are
        !          2949:  left unchanged.  This command is useful, e.g., to restore the default
        !          2950:  settings at the end of a command file, or to return to a defined state after
        !          2951:  lots of settings have been changed within a command file.  Please refer to
        !          2952:  the `set` command to see the default values that the various options take.
        !          2953: 2 save
        !          2954: ?commands save
        !          2955: ?save
        !          2956:  The `save` command saves user-defined functions, variables, `set` options,
        !          2957:  or all three, plus the last `plot` (`splot`) command to the specified file.
        !          2958:
        !          2959:  Syntax:
        !          2960:        save  {<option>} '<filename>'
        !          2961:
        !          2962:  where <option> is `functions`, `variables` or `set`. If no option is used,
        !          2963:  `gnuplot` saves functions, variables, `set` options and the last `plot`
        !          2964:  (`splot`) command.
        !          2965:
        !          2966:  `save`d files are written in text format and may be read by the `load`
        !          2967:  command.
        !          2968:
        !          2969:  The filename must be enclosed in quotes.
        !          2970:
        !          2971:  Examples:
        !          2972:        save 'work.gnu'
        !          2973:        save functions 'func.dat'
        !          2974:        save var 'var.dat'
        !          2975:        save set 'options.dat'
        !          2976: 2 set-show
        !          2977: ?commands set
        !          2978: ?commands show
        !          2979: ?set
        !          2980: ?show
        !          2981: ?show all
        !          2982:  The `set` command can be used to sets _lots_ of options.  No screen is
        !          2983:  drawn, however, until a `plot`, `splot`, or `replot` command is given.
        !          2984:
        !          2985:  The `show` command shows their settings;  `show all` shows all the
        !          2986:  settings.
        !          2987:
        !          2988:  If a variable contains time/date data, `show` will display it according to
        !          2989:  the format currently defined by `set timefmt`, even if that was not in effect
        !          2990:  when the variable was initially defined.
        !          2991: 3 angles
        !          2992: ?commands set angles
        !          2993: ?commands show angles
        !          2994: ?set angles
        !          2995: ?show angles
        !          2996: ?angles
        !          2997: ?commands set angles degrees
        !          2998: ?set angles degrees
        !          2999: ?angles degrees
        !          3000: ?degrees
        !          3001:  By default, `gnuplot` assumes the independent variable in polar graphs is in
        !          3002:  units of radians.  If `set angles degrees` is specified before `set polar`,
        !          3003:  then the default range is [0:360] and the independent variable has units of
        !          3004:  degrees.  This is particularly useful for plots of data files.  The angle
        !          3005:  setting also applies to 3-d mapping as set via the `set mapping` command.
        !          3006:
        !          3007:  Syntax:
        !          3008:        set angles {degrees | radians}
        !          3009:        show angles
        !          3010:
        !          3011:  The angle specified in `set grid polar` is also read and displayed in the
        !          3012:  units specified by `set angles`.
        !          3013:
        !          3014:  `set angles` also affects the arguments of the machine-defined functions
        !          3015:  sin(x), cos(x) and tan(x), and the outputs of asin(x), acos(x), atan(x),
        !          3016:  atan2(x), and arg(x).  It has no effect on the arguments of hyperbolic
        !          3017:  functions or Bessel functions.  However, the output arguments of inverse
        !          3018:  hyperbolic functions of complex arguments are affected; if these functions
        !          3019:  are used, `set angles radians` must be in effect to maintain consistency
        !          3020:  between input and output arguments.
        !          3021:
        !          3022:        x={1.0,0.1}
        !          3023:        set angles radians
        !          3024:        y=sinh(x)
        !          3025:        print y         #prints {1.16933, 0.154051}
        !          3026:        print asinh(y)  #prints {1.0, 0.1}
        !          3027:  but
        !          3028:        set angles degrees
        !          3029:        y=sinh(x)
        !          3030:        print y         #prints {1.16933, 0.154051}
        !          3031:        print asinh(y)  #prints {57.29578, 5.729578}
        !          3032: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/poldat/poldat.html"> Polar plot using `set angles`. </a>
        !          3033: 3 arrow
        !          3034: ?commands set arrow
        !          3035: ?commands set noarrow
        !          3036: ?commands show arrow
        !          3037: ?set arrow
        !          3038: ?set noarrow
        !          3039: ?show arrow
        !          3040: ?arrow
        !          3041: ?noarrow
        !          3042:  Arbitrary arrows can be placed on a plot using the `set arrow` command.
        !          3043:
        !          3044:  Syntax:
        !          3045:        set arrow {<tag>} {from <position>} {to <position>} {{no}head}
        !          3046:                  { {linestyle | ls <line_style>}
        !          3047:                    | {linetype | lt <line_type>}
        !          3048:                      {linewidth | lw <line_width} }
        !          3049:        set noarrow {<tag>}
        !          3050:        show arrow
        !          3051:
        !          3052:  <tag> is an integer that identifies the arrow.  If no tag is given, the
        !          3053:  lowest unused tag value is assigned automatically.  The tag can be used to
        !          3054:  delete or change a specific arrow.  To change any attribute of an existing
        !          3055:  arrow, use the `set arrow` command with the appropriate tag and specify the
        !          3056:  parts of the arrow to be changed.
        !          3057:
        !          3058:  The <position>s are specified by either x,y or x,y,z, and may be preceded by
        !          3059:  `first`, `second`, `graph`, or `screen` to select the coordinate system.
        !          3060:  Unspecified coordinates default to 0.  The endpoints can be specified in
        !          3061:  one of four coordinate systems---`first` or `second` axes, `graph` or
        !          3062:  `screen`.  See `coordinates` for details.  A coordinate system specifier
        !          3063:  does not carry over from the "from" position to the "to" position.  Arrows
        !          3064:  outside the screen boundaries are permitted but may cause device errors.
        !          3065:
        !          3066:  Specifying `nohead` produces an arrow drawn without a head---a line segment.
        !          3067:  This gives you yet another way to draw a line segment on the plot.  By
        !          3068:  default, arrows have heads.
        !          3069:
        !          3070:  The line style may be selected from a user-defined list of line styles (see
        !          3071:  `set linestyle`) or may be defined here by providing values for <line_type>
        !          3072:  (an index from the default list of styles) and/or <line_width> (which is a
        !          3073:  multiplier for the default width).
        !          3074:
        !          3075:  Note, however, that if a user-defined line style has been selected, its
        !          3076:  properties (type and width) cannot be altered merely by issuing another
        !          3077:  `set arrow` command with the appropriate index and `lt` or `lw`.
        !          3078:
        !          3079:  Examples:
        !          3080:
        !          3081:  To set an arrow pointing from the origin to (1,2) with user-defined style 5,
        !          3082:  use:
        !          3083:        set arrow to 1,2 ls 5
        !          3084:
        !          3085:  To set an arrow from bottom left of plotting area to (-5,5,3), and tag the
        !          3086:  arrow number 3, use:
        !          3087:        set arrow 3 from graph 0,0 to -5,5,3
        !          3088:
        !          3089:  To change the preceding arrow to end at 1,1,1, without an arrow head and
        !          3090:  double its width, use:
        !          3091:        set arrow 3 to 1,1,1 nohead lw 2
        !          3092:
        !          3093:  To draw a vertical line from the bottom to the top of the graph at x=3, use:
        !          3094:        set arrow from 3, graph 0 to 3, graph 1 nohead
        !          3095:
        !          3096:  To delete arrow number 2, use:
        !          3097:        set noarrow 2
        !          3098:
        !          3099:  To delete all arrows, use:
        !          3100:        set noarrow
        !          3101:
        !          3102:  To show all arrows (in tag order), use:
        !          3103:        show arrow
        !          3104: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/arrows/arrows.html"> Arrows Demos. </a>
        !          3105: 3 autoscale
        !          3106: ?commands set autoscale
        !          3107: ?commands set noautoscale
        !          3108: ?commands show autoscale
        !          3109: ?set autoscale
        !          3110: ?set noautoscale
        !          3111: ?show autoscale
        !          3112: ?autoscale
        !          3113: ?noautoscale
        !          3114:  Autoscaling may be set individually on the x, y or z axis or globally on all
        !          3115:  axes. The default is to autoscale all axes.
        !          3116:
        !          3117:  Syntax:
        !          3118:        set autoscale {<axes>{min|max}}
        !          3119:        set noautoscale {<axes>{min|max}}
        !          3120:        show autoscale
        !          3121:
        !          3122:  where <axes> is either `x`, `y`, `z`, `x2`, `y2` or `xy`.  A keyword with
        !          3123:  `min` or `max` appended (this cannot be done with `xy`) tells `gnuplot` to
        !          3124:  autoscale just the minimum or maximum of that axis.  If no keyword is given,
        !          3125:  all axes are autoscaled.
        !          3126:
        !          3127:  When autoscaling, the axis range is automatically computed and the dependent
        !          3128:  axis (y for a `plot` and z for `splot`) is scaled to include the range of the
        !          3129:  function or data being plotted.
        !          3130:
        !          3131:  If autoscaling of the dependent axis (y or z) is not set, the current y or z
        !          3132:  range is used.
        !          3133:
        !          3134:  Autoscaling the independent variables (x for `plot` and x,y for `splot`) is a
        !          3135:  request to set the domain to match any data file being plotted.  If there are
        !          3136:  no data files, autoscaling an independent variable has no effect.  In other
        !          3137:  words, in the absence of a data file, functions alone do not affect the x
        !          3138:  range (or the y range if plotting z = f(x,y)).
        !          3139:
        !          3140:  Please see `set xrange` for additional information about ranges.
        !          3141:
        !          3142:  The behavior of autoscaling remains consistent in parametric mode, (see `set
        !          3143:  parametric`).  However, there are more dependent variables and hence more
        !          3144:  control over x, y, and z axis scales.  In parametric mode, the independent or
        !          3145:  dummy variable is t for `plot`s and u,v for `splot`s.  `autoscale` in
        !          3146:  parametric mode, then, controls all ranges (t, u, v, x, y, and z) and allows
        !          3147:  x, y, and z to be fully autoscaled.
        !          3148:
        !          3149:  Autoscaling works the same way for polar mode as it does for parametric mode
        !          3150:  for `plot`, with the extension that in polar mode `set dummy` can be used to
        !          3151:  change the independent variable from t (see `set dummy`).
        !          3152:
        !          3153:  When tics are displayed on second axes but no plot has been specified for
        !          3154:  those axes, x2range and y2range are inherited from xrange and yrange.  This
        !          3155:  is done _before_ xrange and yrange are autoextended to a whole number of
        !          3156:  tics, which can cause unexpected results.
        !          3157:
        !          3158:  Examples:
        !          3159:
        !          3160:  This sets autoscaling of the y axis (other axes are not affected):
        !          3161:        set autoscale y
        !          3162:
        !          3163:  This sets autoscaling only for the minimum of the y axis (the maximum of the
        !          3164:  y axis and the other axes are not affected):
        !          3165:        set autoscale ymin
        !          3166:
        !          3167:  This sets autoscaling of the x and y axes:
        !          3168:        set autoscale xy
        !          3169:
        !          3170:  This sets autoscaling of the x, y, z, x2 and y2 axes:
        !          3171:        set autoscale
        !          3172:
        !          3173:  This disables autoscaling of the x, y, z, x2 and y2 axes:
        !          3174:        set noautoscale
        !          3175:
        !          3176:  This disables autoscaling of the z axis only:
        !          3177:        set noautoscale z
        !          3178: 4 parametric mode
        !          3179: ?commands set autoscale parametric
        !          3180: ?set autoscale parametric
        !          3181: ?set autoscale t
        !          3182:  When in parametric mode (`set parametric`), the xrange is as fully scalable
        !          3183:  as the y range.  In other words, in parametric mode the x axis can be
        !          3184:  automatically scaled to fit the range of the parametric function that is
        !          3185:  being plotted.  Of course, the y axis can also be automatically scaled just
        !          3186:  as in the non-parametric case.  If autoscaling on the x axis is not set, the
        !          3187:  current x range is used.
        !          3188:
        !          3189:  Data files are plotted the same in parametric and non-parametric mode.
        !          3190:  However, there is a difference in mixed function and data plots: in
        !          3191:  non-parametric mode with autoscaled x, the x range of the datafile controls
        !          3192:  the x range of the functions; in parametric mode it has no influence.
        !          3193:
        !          3194:  For completeness a last command `set autoscale t` is accepted.  However, the
        !          3195:  effect of this "scaling" is very minor.  When `gnuplot` determines that the
        !          3196:  t range would be empty, it makes a small adjustment if autoscaling is true.
        !          3197:  Otherwise, `gnuplot` gives an error.  Such behavior may, in fact, not be very
        !          3198:  useful and the command `set autoscale t` is certainly questionable.
        !          3199:
        !          3200:  `splot` extends the above ideas as you would expect.  If autoscaling is set,
        !          3201:  then x, y, and z ranges are computed and each axis scaled to fit the
        !          3202:  resulting data.
        !          3203: 4 polar mode
        !          3204: ?commands set autoscale polar
        !          3205: ?set autoscale polar
        !          3206: ?set autoscale t
        !          3207:  When in polar mode (`set polar`), the xrange and the yrange are both found
        !          3208:  from the polar coordinates, and thus they can both be automatically scaled.
        !          3209:  In other words, in polar mode both the x and y axes can be automatically
        !          3210:  scaled to fit the ranges of the polar function that is being plotted.
        !          3211:
        !          3212:  When plotting functions in polar mode, the rrange may be autoscaled.  When
        !          3213:  plotting data files in polar mode, the trange may also be autoscaled.  Note
        !          3214:  that if the trange is contained within one quadrant, autoscaling will produce
        !          3215:  a polar plot of only that single quadrant.
        !          3216:
        !          3217:  Explicitly setting one or two ranges but not others may lead to unexpected
        !          3218:  results.
        !          3219: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/poldat/poldat.html"> See polar demos </a>
        !          3220: 3 bar
        !          3221: ?commands set bar
        !          3222: ?commands show bar
        !          3223: ?set bar
        !          3224: ?show bar
        !          3225:  The `set bar` command controls the tics at the ends of errorbars.
        !          3226:
        !          3227:  Syntax:
        !          3228:        set bar {small | large | <size>}
        !          3229:        show bar
        !          3230:
        !          3231:  `small` is a synonym for 0.0, and `large` for 1.0.
        !          3232:  The default is 1.0 if no size is given.
        !          3233: 3 bmargin
        !          3234: ?commands set bmargin
        !          3235: ?set bmargin
        !          3236: ?bmargin
        !          3237:  The command `set bmargin` sets the size of the bottom margin.  Please see
        !          3238:  `set margin` for details.
        !          3239: 3 border
        !          3240: ?commands set border
        !          3241: ?commands set noborder
        !          3242: ?commands show border
        !          3243: ?set border
        !          3244: ?set noborder
        !          3245: ?show border
        !          3246: ?border
        !          3247: ?noborder
        !          3248:  The `set border` and `set noborder` commands control the display of the graph
        !          3249:  borders for the `plot` and `splot` commands.
        !          3250:
        !          3251:  Syntax:
        !          3252:        set border {<integer> { {linestyle | ls <line_style>}
        !          3253:                                | {linetype | lt <line_type> }
        !          3254:                                  {linewidth | lw <line_width>} } }
        !          3255:        set noborder
        !          3256:        show border
        !          3257:
        !          3258:  The borders are encoded in a 12-bit integer: the bottom four bits control the
        !          3259:  border for `plot` and the sides of the base for `splot`; The next four bits
        !          3260:  control the verticals in `splot`; the top four bits control the edges on top
        !          3261:  of the `splot`.  In detail, the `<integer>` should be the sum of the
        !          3262:  appropriate entries from the following table:
        !          3263:
        !          3264: @start table - first is interactive cleartext form
        !          3265:                          plot border     splot         splot
        !          3266:            Side          splot base    verticals        top
        !          3267:        bottom (south)         1            16           256
        !          3268:        left   (west)          2            32           512
        !          3269:        top    (north)         4            64          1024
        !          3270:        right  (east)          8           128          2048
        !          3271: #\begin{tabular}{|cc|ccc|} \hline
        !          3272: #\multicolumn{5}{|c|}{Graph Border Encoding} \\ \hline \hline
        !          3273: # & & \multicolumn{3}{|c|}{Integer value of selection bit} \\ \cline{3-5}
        !          3274: # & & plot border & splot & splot \\
        !          3275: #\multicolumn{2}{|c|}{Side}& splot base & verticals & top \\ \hline
        !          3276: #bottom & (south) & 1 & 16 & 256 \\
        !          3277: #left   & (west)  & 2 & 32 & 512 \\
        !          3278: #top    & (north) & 4 & 64 & 1024 \\
        !          3279: #right  & (east)  & 8 & 128 & 2048 \\
        !          3280: %c c c c c .
        !          3281: %@plot border@splot@splot
        !          3282: %@splot base@verticals@top
        !          3283: %_
        !          3284: %bottom (south)@1@16@256
        !          3285: %left   (west)@2@32@512
        !          3286: %top    (north)@4@64@1024
        !          3287: %right  (east)@8@128@2048
        !          3288: @end table
        !          3289:
        !          3290:  The default is 31, which is all four sides for `plot`, and base and z axis
        !          3291:  for `splot`.
        !          3292:
        !          3293:  Using the optional <line_style>, <line_type> and <line_width>
        !          3294:  specifiers, the way the border lines are drawn can be influenced
        !          3295:  (limited by what the current terminal driver supports).
        !          3296:
        !          3297:  Various axes or combinations of axes may be added together in the command.
        !          3298:
        !          3299:  To have tics on edges other than bottom and left, disable the usual tics and
        !          3300:  enable the second axes.
        !          3301:
        !          3302:  Examples:
        !          3303:
        !          3304:  Draw all borders:
        !          3305:        set border
        !          3306:
        !          3307:  Draw only the SOUTHWEST borders:
        !          3308:        set border 3
        !          3309:
        !          3310:  Draw a complete box around a `splot`:
        !          3311:        set border 4095
        !          3312:
        !          3313:  Draw a partial box, omitting the front vertical:
        !          3314:        set border 127+256+512
        !          3315:
        !          3316:  Draw only the NORTHEAST borders:
        !          3317:        set noxtics; set noytics; set x2tics; set y2tics; set border 12
        !          3318:
        !          3319: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/borders/borders.html"> Borders Demo. </a>
        !          3320: 3 boxwidth
        !          3321: ?commands set boxwidth
        !          3322: ?commands show boxwidth
        !          3323: ?set boxwidth
        !          3324: ?show boxwidth
        !          3325: ?boxwidth
        !          3326:  The `set boxwidth` command is used to set the default width of boxes in the
        !          3327:  `boxes` and `boxerrorbars` styles.
        !          3328:
        !          3329:  Syntax:
        !          3330:        set boxwidth {<width>}
        !          3331:        show boxwidth
        !          3332:
        !          3333:  If a data file is plotted without the width being specified in the third,
        !          3334:  fourth, or fifth column (or `using` entry), or if a function is plotted, the
        !          3335:  width of each box is set by the `set boxwidth` command.  (If a width is given
        !          3336:  both in the file and by the `set boxwidth` command, the one in the file is
        !          3337:  used.)  If the width is not specified in one of these ways, the width of each
        !          3338:  box will be calculated automatically so that it touches the adjacent boxes.
        !          3339:  In a four-column data set, the fourth column will be interpreted as the box
        !          3340:  width unless the width is set to -2.0, in which case the width will be
        !          3341:  calculated automatically.  See `set style boxerrorbars` for more details.
        !          3342:
        !          3343:  To set the box width to automatic use the command
        !          3344:        set boxwidth
        !          3345:  or, for four-column data,
        !          3346:        set boxwidth -2
        !          3347:
        !          3348:  The same effect can be achieved with the `using` keyword in `plot`:
        !          3349:        plot 'file' using 1:2:3:4:(-2)
        !          3350: 3 clabel
        !          3351: ?commands set clabel
        !          3352: ?commands set noclabel
        !          3353: ?commands show clabel
        !          3354: ?set clabel
        !          3355: ?set noclabel
        !          3356: ?show clabel
        !          3357: ?clabel
        !          3358: ?noclabel
        !          3359:  `gnuplot` will vary the linetype used for each contour level when clabel is
        !          3360:  set.  When this option on (the default), a legend labels each linestyle with
        !          3361:  the z level it represents.  It is not possible at present to separate the
        !          3362:  contour labels from the surface key.
        !          3363:
        !          3364:  Syntax:
        !          3365:        set clabel {'<format>'}
        !          3366:        set noclabel
        !          3367:        show clabel
        !          3368:
        !          3369:  The default for the format string is %8.3g, which gives three decimal places.
        !          3370:  This may produce poor label alignment if the key is altered from its default
        !          3371:  configuration.
        !          3372:
        !          3373:  The first contour linetype, or only contour linetype when clabel is off, is
        !          3374:  the surface linetype +1; contour points are the same style as surface points.
        !          3375:
        !          3376:  See also `set contour`.
        !          3377: 3 clip
        !          3378: ?commands set clip
        !          3379: ?commands set noclip
        !          3380: ?commands show clip
        !          3381: ?set clip
        !          3382: ?set noclip
        !          3383: ?show clip
        !          3384: ?clip
        !          3385: ?noclip
        !          3386:  `gnuplot` can clip data points and lines that are near the boundaries of a
        !          3387:  graph.
        !          3388:
        !          3389:  Syntax:
        !          3390:        set clip <clip-type>
        !          3391:        set noclip <clip-type>
        !          3392:        show clip
        !          3393:
        !          3394:  Three clip types are supported by `gnuplot`: `points`, `one`, and `two`.
        !          3395:  One, two, or all three clip types may be active for a single graph.
        !          3396:
        !          3397:  The `points` clip type forces `gnuplot` to clip (actually, not plot at all)
        !          3398:  data points that fall within but too close to the boundaries.  This is done
        !          3399:  so that large symbols used for points will not extend outside the boundary
        !          3400:  lines.  Without clipping points near the boundaries, the plot may look bad.
        !          3401:  Adjusting the x and y ranges may give similar results.
        !          3402:
        !          3403:  Setting the `one` clip type causes `gnuplot` to draw a line segment which has
        !          3404:  only one of its two endpoints within the graph.  Only the in-range portion of
        !          3405:  the line is drawn.  The alternative is to not draw any portion of the line
        !          3406:  segment.
        !          3407:
        !          3408:  Some lines may have both endpoints out of range, but pass through the graph.
        !          3409:  Setting the `two` clip-type allows the visible portion of these lines to be
        !          3410:  drawn.
        !          3411:
        !          3412:  In no case is a line drawn outside the graph.
        !          3413:
        !          3414:  The defaults are `noclip points`, `clip one`, and `noclip two`.
        !          3415:
        !          3416:  To check the state of all forms of clipping, use
        !          3417:        show clip
        !          3418:
        !          3419:  For backward compatibility with older versions, the following forms are also
        !          3420:  permitted:
        !          3421:        set clip
        !          3422:        set noclip
        !          3423:
        !          3424:  `set clip` is synonymous with `set clip points`; `set noclip` turns off all
        !          3425:  three types of clipping.
        !          3426: 3 cntrparam
        !          3427: ?commands set cntrparam
        !          3428: ?commands show cntrparam
        !          3429: ?set cntrparam
        !          3430: ?show cntrparam
        !          3431: ?cntrparam
        !          3432:  `set cntrparam` controls the generation of contours and their smoothness for
        !          3433:  a contour plot. `show contour` displays current settings of `cntrparam` as
        !          3434:  well as `contour`.
        !          3435:
        !          3436:  Syntax:
        !          3437:        set cntrparam {  {linear | cubicspline | bspline}
        !          3438:                        { points <n>} { order <n> }
        !          3439:                        { levels   auto {<n>} | <n>
        !          3440:                                 | discrete <z1> {,<z2>{,<z3>...}}
        !          3441:                                 | incremental <start>, <incr> {,<end>}
        !          3442:                         }
        !          3443:                       }
        !          3444:        show contour
        !          3445:
        !          3446:  This command has two functions.  First, it sets the values of z for which
        !          3447:  contour points are to be determined (by linear interpolation between data
        !          3448:  points or function isosamples.)  Second, it controls the way contours are
        !          3449:  drawn between the points determined to be of equal z.  <n> should be an
        !          3450:  integral constant expression and <z1>, <z2> ... any constant expressions.
        !          3451:  The parameters are:
        !          3452:
        !          3453:  `linear`, `cubicspline`, `bspline`---Controls type of approximation or
        !          3454:  interpolation.  If `linear`, then straight line segments connect points of
        !          3455:  equal z magnitude.  If `cubicspline`, then piecewise-linear contours are
        !          3456:  interpolated between the same equal z points to form somewhat smoother
        !          3457:  contours, but which may undulate.  If `bspline`, a guaranteed-smoother curve
        !          3458:  is drawn, which only approximates the position of the points of equal-z.
        !          3459:
        !          3460:  `points`---Eventually all drawings are done with piecewise-linear strokes.
        !          3461:  This number controls the number of line segments used to approximate the
        !          3462:  `bspline` or `cubicspline` curve.  Number of cubicspline or bspline
        !          3463:  segments (strokes) = `points` * number of linear segments.
        !          3464:
        !          3465:  `order`---Order of the bspline approximation to be used.  The bigger this
        !          3466:  order is, the smoother the resulting contour.  (Of course, higher order
        !          3467:  bspline curves will move further away from the original piecewise linear
        !          3468:  data.)  This option is relevant for `bspline` mode only.  Allowed values are
        !          3469:  integers in the range from 2 (linear) to 10.
        !          3470:
        !          3471:  `levels`--- Selection of contour levels,  controlled by `auto` (default),
        !          3472:  `discrete`, `incremental`, and <n>, number of contour levels, limited to
        !          3473:   MAX_DISCRETE_LEVELS as defined in plot.h (30 is standard.)
        !          3474:
        !          3475:  For `auto`, <n> specifies a nominal number of levels; the actual number will
        !          3476:  be adjusted to give simple labels. If the surface is bounded by zmin and zmax,
        !          3477:  contours will be generated at integer multiples of dz between zmin and zmax,
        !          3478:  where dz is 1, 2, or 5 times some power of ten (like the step between two
        !          3479:  tic marks).
        !          3480:
        !          3481:  For `levels discrete`, contours will be generated at z = <z1>, <z2> ... as
        !          3482:  specified; the number of discrete levels sets the number of contour levels.
        !          3483:  In `discrete` mode, any `set cntrparms levels <n>` are ignored.
        !          3484:
        !          3485:  For `incremental`, contours are generated at values of z beginning at <start>
        !          3486:  and increasing by <increment>, until the number of contours is reached. <end>
        !          3487:  is used to determine the number of contour levels, which will be changed by
        !          3488:  any subsequent `set cntrparam levels <n>`.
        !          3489:
        !          3490:  If the command `set cntrparam` is given without any arguments specified,  the
        !          3491:  defaults are used: linear, 5 points, order 4, 5 auto levels.
        !          3492:
        !          3493:  Examples:
        !          3494:        set cntrparam bspline
        !          3495:        set cntrparam points 7
        !          3496:        set cntrparam order 10
        !          3497:
        !          3498:  To select levels automatically, 5 if the level increment criteria are met:
        !          3499:        set cntrparam levels auto 5
        !          3500:
        !          3501:  To specify discrete levels at .1, .37, and .9:
        !          3502:        set cntrparam levels discrete .1,1/exp(1),.9
        !          3503:
        !          3504:  To specify levels from 0 to 4 with increment 1:
        !          3505:        set cntrparam levels incremental  0,1,4
        !          3506:
        !          3507:  To set the number of levels to 10 (changing an incremental end or possibly
        !          3508:  the number of auto levels):
        !          3509:        set cntrparam levels 10
        !          3510:
        !          3511:  To set the start and increment while retaining the number of levels:
        !          3512:        set cntrparam levels incremental 100,50
        !          3513:
        !          3514:  See also `set contour` for control of where the contours are drawn, and `set
        !          3515:  clabel` for control of the format of the contour labels and linetypes.
        !          3516: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/contours/contours.html">Contours Demo</a> and
        !          3517: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/discrete/discrete.html">contours with User Defined Levels.</a>
        !          3518: 3 contour
        !          3519: ?commands set contour
        !          3520: ?commands set nocontour
        !          3521: ?commands show contour
        !          3522: ?set contour
        !          3523: ?set nocontour
        !          3524: ?show contour
        !          3525: ?contour
        !          3526: ?nocontour
        !          3527:  `set contour` enables contour drawing for surfaces. This option is available
        !          3528:  for `splot` only.
        !          3529:
        !          3530:  Syntax:
        !          3531:        set contour {base | surface | both}
        !          3532:        set nocontour
        !          3533:        show contour
        !          3534:
        !          3535:  The three options specify where to draw the contours: `base` draws the
        !          3536:  contours on the grid base where the x/ytics are placed, `surface` draws the
        !          3537:  contours on the surfaces themselves, and `both` draws the contours on both
        !          3538:  the base and the surface.  If no option is provided, the default is `base`.
        !          3539:
        !          3540:  See also `set cntrparam` for the parameters that affect the drawing of
        !          3541:  contours, and `set clabel` for control of labelling of the contours.
        !          3542:
        !          3543:  The surface can be switched off (see `set surface`), giving a contour-only
        !          3544:  graph.  Though it is possible to use `set size` to enlarge the plot to fill
        !          3545:  the screen, more control over the output format can be obtained by writing
        !          3546:  the contour information to a file, and rereading it as a 2-d datafile plot:
        !          3547:
        !          3548:        set nosurface
        !          3549:        set contour
        !          3550:        set cntrparam ...
        !          3551:        set term table
        !          3552:        set out 'filename'
        !          3553:        splot ...
        !          3554:        set out
        !          3555:        # contour info now in filename
        !          3556:        set term <whatever>
        !          3557:        plot 'filename'
        !          3558:
        !          3559:  In order to draw contours, the data should be organized as "grid data".  In
        !          3560:  such a file all the points for a single y-isoline are listed, then all the
        !          3561:  points for the next y-isoline, and so on.  A single blank line (a line
        !          3562:  containing no characters other than blank spaces and a carriage return and/or
        !          3563:  a line feed) separates one y-isoline from the next.  See also `splot datafile`.
        !          3564:
        !          3565:  If contours are desired from non-grid data, `set dgrid3d` can be used to
        !          3566:  create an appropriate grid.  See `set dgrid3d` for more information.
        !          3567: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/contours/contours.html">Contours Demo</a> and
        !          3568: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/discrete/discrete.html">contours with User Defined Levels.</a>
        !          3569: 3 data style
        !          3570: ?commands set data style
        !          3571: ?commands show data style
        !          3572: ?set data style
        !          3573: ?show data style
        !          3574: ?data style
        !          3575:  The `set data style` command changes the default plotting style for data
        !          3576:  plots.
        !          3577:
        !          3578:  Syntax:
        !          3579:        set data style <style-choice>
        !          3580:        show data style
        !          3581:
        !          3582:  See `set style` for the choices.  If no choice is given, the choices are
        !          3583:  listed.  `show data style` shows the current default data plotting style.
        !          3584: 3 dgrid3d
        !          3585: ?commands set dgrid3d
        !          3586: ?commands set nodgrid3d
        !          3587: ?commands show dgrid3d
        !          3588: ?set dgrid3d
        !          3589: ?set nodgrid3d
        !          3590: ?show dgrid3d
        !          3591: ?dgrid3d
        !          3592: ?nodgrid3d
        !          3593:  The `set dgrid3d` command enables, and can set parameters for, non-grid
        !          3594:  to grid data mapping.
        !          3595:
        !          3596:  Syntax:
        !          3597:        set dgrid3d {<row_size>} {,{<col_size>} {,<norm>}}
        !          3598:        set nodgrid3d
        !          3599:        show dgrid3d
        !          3600:
        !          3601:  By default `dgrid3d` is disabled.  When enabled, 3-d data read from a file
        !          3602:  are always treated as a scattered data set.  A grid with dimensions derived
        !          3603:  from a bounding box of the scattered data and size as specified by the
        !          3604:  row/col_size parameters is created for plotting and contouring.  The grid
        !          3605:  is equally spaced in x (rows) and in y (columns); the z values are computed
        !          3606:  as weighted averages of the scattered points' z values.
        !          3607:
        !          3608:  The third parameter, norm, controls the weighting:  Each data point is
        !          3609:  weighted inversely by its distance from the grid point raised to the norm
        !          3610:  power.  (Actually, the weights are given by the inverse of dx^norm + dy^norm,
        !          3611:  where dx and dy are the components of the separation of the grid point from
        !          3612:  each data point.  For some norms that are powers of two, specifically 4, 8,
        !          3613:  and 16, the computation is optimized by using the Euclidean distance in the
        !          3614:  weight calculation, (dx^2+dx^2)^norm/2.  However, any non-negative integer
        !          3615:  can be used.)
        !          3616:
        !          3617:  The closer the data point is to a grid point, the more effect it has on
        !          3618:  that grid point and the larger the value of norm the less effect more
        !          3619:  distant data points have on that grid point.
        !          3620:
        !          3621:  The `dgrid3d` option is a simple low pass filter that converts scattered
        !          3622:  data to a grid data set.  More sophisticated approaches to this problem
        !          3623:  exist and should be used to preprocess the data outside `gnuplot` if this
        !          3624:  simple solution is found inadequate.
        !          3625:
        !          3626:  (The z values are found by weighting all data points, not by interpolating
        !          3627:  between nearby data points;  also edge effects may produce unexpected and/or
        !          3628:  undesired results.  In some cases, small norm values produce a grid point
        !          3629:  reflecting the average of distant data points rather than a local average,
        !          3630:  while large values of norm may produce "steps" with several grid points
        !          3631:  having the same value as the closest data point, rather than making a smooth
        !          3632:  transition between adjacent data points.  Some areas of a grid may be filled
        !          3633:  by extrapolation, to an arbitrary boundary condition.  The variables are
        !          3634:  not normalized; consequently the units used for x and y will affect the
        !          3635:  relative weights of points in the x and y directions.)
        !          3636:
        !          3637:  Examples:
        !          3638:        set dgrid3d 10,10,1     # defaults
        !          3639:        set dgrid3d ,,4
        !          3640:
        !          3641:  The first specifies that a grid of size 10 by 10 is to be constructed using
        !          3642:  a norm value of 1 in the weight computation.  The second only modifies the
        !          3643:  norm, changing it to 4.
        !          3644: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/scatter/scatter.html"> Dgrid3d Demo.</a>
        !          3645:
        !          3646: 3 dummy
        !          3647: ?commands set dummy
        !          3648: ?commands show dummy
        !          3649: ?set dummy
        !          3650: ?show dummy
        !          3651: ?dummy
        !          3652:  The `set dummy` command changes the default dummy variable names.
        !          3653:
        !          3654:  Syntax:
        !          3655:        set dummy {<dummy-var>} {,<dummy-var>}
        !          3656:        show dummy
        !          3657:
        !          3658:  By default, `gnuplot` assumes that the independent, or "dummy", variable for
        !          3659:  the `plot` command is "t" if in parametric or polar mode, or "x" otherwise.
        !          3660:  Similarly the independent variables for the `splot` command are "u" and "v"
        !          3661:  in parametric mode (`splot` cannot be used in polar mode), or "x" and "y"
        !          3662:  otherwise.
        !          3663:
        !          3664:  It may be more convenient to call a dummy variable by a more physically
        !          3665:  meaningful or conventional name.  For example, when plotting time functions:
        !          3666:
        !          3667:        set dummy t
        !          3668:        plot sin(t), cos(t)
        !          3669:
        !          3670:  At least one dummy variable must be set on the command; `set dummy` by itself
        !          3671:  will generate an error message.
        !          3672:
        !          3673:  Examples:
        !          3674:        set dummy u,v
        !          3675:        set dummy ,s
        !          3676:
        !          3677:  The second example sets the second variable to s.
        !          3678: 3 encoding
        !          3679: ?commands set encoding
        !          3680: ?commands show encoding
        !          3681: ?set encoding
        !          3682: ?show encoding
        !          3683: ?encoding
        !          3684:  The `set encoding` command selects a character encoding.  Valid values are
        !          3685:  `default`, which tells a terminal to use its default; `iso_8859_1` (known in
        !          3686:  the PostScript world as `ISO-Latin1`), which is used on many Unix workstations
        !          3687:  and with MS-Windows; `cp850`, for OS/2; and `cp437`, for MS-DOS.
        !          3688:
        !          3689:  Syntax:
        !          3690:        set encoding {<value>}
        !          3691:        show encoding
        !          3692:
        !          3693:  Note that encoding is not supported by all terminal drivers and that
        !          3694:  the device must be able to produce the desired non-standard characters.
        !          3695: 3 format
        !          3696: ?commands set format
        !          3697: ?commands show format
        !          3698: ?set format
        !          3699: ?show format
        !          3700: ?format
        !          3701:  The format of the tic-mark labels can be set with the `set format` command.
        !          3702:
        !          3703:  Syntax:
        !          3704:        set format {<axes>} {"<format-string>"}
        !          3705:        set format {<axes>} {'<format-string>'}
        !          3706:        show format
        !          3707:
        !          3708:  where <axes> is either `x`, `y`, `z`, `xy`, `x2`, `y2` or nothing (which is
        !          3709:  the same as `xy`).  The length of the string representing a tic mark (after
        !          3710:  formatting with 'printf') is restricted to 100 characters.  If the format
        !          3711:  string is omitted, the format will be returned to the default "%g".  For
        !          3712:  LaTeX users, the format "$%g$" is often desirable.  If the empty string "" is
        !          3713:  used, no label will be plotted with each tic, though the tic mark will still
        !          3714:  be plotted.  To eliminate all tic marks, use `set noxtics` or `set noytics`.
        !          3715:
        !          3716:  Newline (\n) is accepted in the format string.  Use double-quotes rather than
        !          3717:  single-quotes to enable such interpretation.  See also `syntax`.
        !          3718:
        !          3719:  The default format for both axes is "%g", but other formats such as "%.2f" or
        !          3720:  "%3.0em" are often desirable.  Anything accepted by 'printf' when given a
        !          3721:  double precision number, and accepted by the terminal, will work.  Some other
        !          3722:  options have been added.  If the format string looks like a floating point
        !          3723:  format, then `gnuplot` tries to construct a reasonable format.
        !          3724:
        !          3725:  Characters not preceded by "%" are printed verbatim.  Thus you can include
        !          3726:  spaces and labels in your format string, such as "%g m", which will put " m"
        !          3727:  after each number.  If you want "%" itself, double it: "%g %%".
        !          3728:
        !          3729:  See also `set xtics` for more information about tic labels.
        !          3730: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/electron/electron.html"> See demo. </a>
        !          3731: 4 format specifiers
        !          3732: ?commands set format specifiers
        !          3733: ?set format specifiers
        !          3734: ?format specifiers
        !          3735: ?format_specifiers
        !          3736:  The acceptable formats (if not in time/date mode) are:
        !          3737:
        !          3738: @start table - first is interactive cleartext form
        !          3739:        Format       Explanation
        !          3740:        %f           floating point notation
        !          3741:        %e or %E     exponential notation; an "e" or "E" before the power
        !          3742:        %g or %G     the shorter of %e (or %E) and %f
        !          3743:        %x or %X     hex
        !          3744:        %o or %O     octal
        !          3745:        %t           mantissa to base 10
        !          3746:        %l           mantissa to base of current logscale
        !          3747:        %s           mantissa to base of current logscale; scientific power
        !          3748:        %T           power to base 10
        !          3749:        %L           power to base of current logscale
        !          3750:        %S           scientific power
        !          3751:        %c           character replacement for scientific power
        !          3752:        %P           multiple of pi
        !          3753: #\begin{tabular}{|cl|} \hline
        !          3754: #\multicolumn{2}{|c|}{Tic-mark label numerical format specifiers}\\
        !          3755: #\hline \hline
        !          3756: #Format & Explanation \\ \hline
        !          3757: #\verb@%f@ & floating point notation \\
        !          3758: #\verb@%e@ or \verb@%E@ & exponential notation; an "e" or "E" before the power \\
        !          3759: #\verb@%g@ or \verb@%G@ & the shorter of \verb@%e@ (or \verb@%E@) and \verb@%f@ \\
        !          3760: #\verb@%x@ or \verb@%X@ & hex \\
        !          3761: #\verb@%o@ or \verb@%O@ & octal \\
        !          3762: #\verb@%t@ & mantissa to base 10 \\
        !          3763: #\verb@%l@ & mantissa to base of current logscale \\
        !          3764: #\verb@%s@ & mantissa to base of current logscale; scientific power \\
        !          3765: #\verb@%T@ & power to base 10 \\
        !          3766: #\verb@%L@ & power to base of current logscale \\
        !          3767: #\verb@%S@ & scientific power \\
        !          3768: #\verb@%c@ & character replacement for scientific power \\
        !          3769: #\verb@%P@ & multiple of pi \\
        !          3770: %c l .
        !          3771: %Format@Explanation
        !          3772: %_
        !          3773: %%f@floating point notation
        !          3774: %%e or %E@exponential notation; an "e" or "E" before the power
        !          3775: %%g or %G@the shorter of %e (or %E) and %f
        !          3776: %%x or %X@hex
        !          3777: %%o or %O@octal
        !          3778: %%t@mantissa to base 10
        !          3779: %%l@mantissa to base of current logscale
        !          3780: %%s@mantissa to base of current logscale; scientific power
        !          3781: %%T@power to base 10
        !          3782: %%L@power to base of current logscale
        !          3783: %%S@scientific power
        !          3784: %%c@character replacement for scientific power
        !          3785: %%P@multiple of pi
        !          3786: %_
        !          3787: @end table
        !          3788:
        !          3789:  A 'scientific' power is one such that the exponent is a multiple of three.
        !          3790:  Character replacement of scientific powers (`"%c"`) has been implemented
        !          3791:  for powers in the range -18 to +18.  For numbers outside of this range the
        !          3792:  format reverts to exponential.
        !          3793:
        !          3794:  Other acceptable modifiers (which come after the "%" but before the format
        !          3795:  specifier) are "-", which left-justifies the number; "+", which forces all
        !          3796:  numbers to be explicitly signed; "#", which places a decimal point after
        !          3797:  floats that have only zeroes following the decimal point; a positive integer,
        !          3798:  which defines the field width; "0" (the digit, not the letter) immediately
        !          3799:  preceding the field width, which indicates that leading zeroes are to be used
        !          3800:  instead of leading blanks; and a decimal point followed by a non-negative
        !          3801:  integer, which defines the precision (the minimum number of digits of an
        !          3802:  integer, or the number of digits following the decimal point of a float).
        !          3803:
        !          3804:  Some releases of 'printf' may not support all of these modifiers but may also
        !          3805:  support others; in case of doubt, check the appropriate documentation and
        !          3806:  then experiment.
        !          3807:
        !          3808:  Examples:
        !          3809:        set format y "%t"; set ytics (5,10)          # "5.0" and "1.0"
        !          3810:        set format y "%s"; set ytics (500,1000)      # "500" and "1.0"
        !          3811:        set format y "+-12.3f"; set ytics(12345)     # "+12345.000  "
        !          3812:        set format y "%.2t*10^%+03T"; set ytic(12345)# "1.23*10^+04"
        !          3813:        set format y "%s*10^{%S}"; set ytic(12345)   # "12.345*10^{3}"
        !          3814:        set format y "%s %cg"; set ytic(12345)       # "12.345 kg"
        !          3815:        set format y "%.0P pi"; set ytic(6.283185)   # "2 pi"
        !          3816:        set format y "%.0P%%"; set ytic(50)          # "50%"
        !          3817:
        !          3818:        set log y 2; set format y '%l'; set ytics (1,2,3)
        !          3819:        #displays "1.0", "1.0" and "1.5" (since 3 is 1.5 * 2^1)
        !          3820:
        !          3821:  There are some problem cases that arise when numbers like 9.999 are printed
        !          3822:  with a format that requires both rounding and a power.
        !          3823:
        !          3824:  If the data type for the axis is time/date, the format string must contain
        !          3825:  valid codes for the 'strftime' function (outside of `gnuplot`, type "man
        !          3826:  strftime").  See `set timefmt` for a list of the allowed input format codes.
        !          3827: 4 time/date specifiers
        !          3828: ?commands set format time/date_specifiers
        !          3829: ?set format time/date_specifiers
        !          3830: ?set time/date_specifiers
        !          3831: ?time/date_specifiers
        !          3832:  In time/date mode, the acceptable formats are:
        !          3833:
        !          3834: @start table - first is interactive cleartext form
        !          3835:        Format       Explanation
        !          3836:        %a           abbreviated name of day of the week
        !          3837:        %A           full name of day of the week
        !          3838:        %b or %h     abbreviated name of the month
        !          3839:        %B           full name of the month
        !          3840:        %d           day of the month, 1--31
        !          3841:        %D           shorthand for "%m/%d/%y"
        !          3842:        %H or %k     hour, 0--24
        !          3843:        %I or %l     hour, 0--12
        !          3844:        %j           day of the year, 1--366
        !          3845:        %m           month, 1--12
        !          3846:        %M           minute, 0--60
        !          3847:        %p           "am" or "pm"
        !          3848:        %r           shorthand for "%I:%M:%S %p"
        !          3849:        %R           shorthand for %H:%M"
        !          3850:        %S           second, 0--60
        !          3851:        %T           shorthand for "%H:%M:%S"
        !          3852:        %U           week of the year (week starts on Sunday)
        !          3853:        %w           day of the week, 0--6 (Sunday = 0)
        !          3854:        %W           week of the year (week starts on Monday)
        !          3855:        %y           year, 0-99
        !          3856:        %Y           year, 4-digit
        !          3857: #\begin{tabular}{|cl|} \hline
        !          3858: #\multicolumn{2}{|c|}{Tic-mark label Date/Time Format Specifiers}\\
        !          3859: #\hline \hline
        !          3860: #Format & Explanation \\ \hline
        !          3861: #\verb@%a@ & abbreviated name of day of the week \\
        !          3862: #\verb@%A@ & full name of day of the week \\
        !          3863: #\verb@%b@ or \verb@%h@ & abbreviated name of the month \\
        !          3864: #\verb@%B@ & full name of the month \\
        !          3865: #\verb@%d@ & day of the month, 1--31 \\
        !          3866: #\verb@%D@ & shorthand for \verb@"%m/%d/%y"@ \\
        !          3867: #\verb@%H@ or \verb@%k@ & hour, 0--24 \\
        !          3868: #\verb@%I@ or \verb@%l@ & hour, 0--12 \\
        !          3869: #\verb@%j@ & day of the year, 1--366 \\
        !          3870: #\verb@%m@ & month, 1--12 \\
        !          3871: #\verb@%M@ & minute, 0--60 \\
        !          3872: #\verb@%p@ & "am" or "pm" \\
        !          3873: #\verb@%r@ & shorthand for \verb@"%I:%M:%S %p"@ \\
        !          3874: #\verb@%R@ & shorthand for \verb@%H:%M"@ \\
        !          3875: #\verb@%S@ & second, 0--60 \\
        !          3876: #\verb@%T@ & shorthand for \verb@"%H:%M:%S"@ \\
        !          3877: #\verb@%U@ & week of the year (week starts on Sunday) \\
        !          3878: #\verb@%w@ & day of the week, 0--6 (Sunday = 0) \\
        !          3879: #\verb@%W@ & week of the year (week starts on Monday) \\
        !          3880: #\verb@%y@ & year, 0-99 \\
        !          3881: #\verb@%Y@ & year, 4-digit \\
        !          3882: %c l .
        !          3883: %Format@Explanation
        !          3884: %_
        !          3885: %%a@abbreviated name of day of the week
        !          3886: %%A@full name of day of the week
        !          3887: %%b or %h@abbreviated name of the month
        !          3888: %%B@full name of the month
        !          3889: %%d@day of the month, 1--31
        !          3890: %%D@shorthand for "%m/%d/%y"
        !          3891: %%H or %k@hour, 0--24
        !          3892: %%I or %l@hour, 0--12
        !          3893: %%j@day of the year, 1--366
        !          3894: %%m@month, 1--12
        !          3895: %%M@minute, 0--60
        !          3896: %%p@"am" or "pm"
        !          3897: %%r@shorthand for "%I:%M:%S %p"
        !          3898: %%R@shorthand for %H:%M"
        !          3899: %%S@second, 0--60
        !          3900: %%T@shorthand for "%H:%M:%S"
        !          3901: %%U@week of the year (week starts on Sunday)
        !          3902: %%w@day of the week, 0--6 (Sunday = 0)
        !          3903: %%W@week of the year (week starts on Monday)
        !          3904: %%y@year, 0-99
        !          3905: %%Y@year, 4-digit
        !          3906: %_
        !          3907: @end table
        !          3908:
        !          3909:  Except for the non-numerical formats, these may be preceded by a "0" ("zero",
        !          3910:  not "oh") to pad the field length with leading zeroes, and a positive digit,
        !          3911:  to define the minimum field width (which will be overridden if the specified
        !          3912:  width is not large enough to contain the number).  There is a 24-character
        !          3913:  limit to the length of the printed text; longer strings will be truncated.
        !          3914:
        !          3915:  Examples:
        !          3916:
        !          3917:  Suppose the text is "76/12/25 23:11:11".  Then
        !          3918:        set format x                 # defaults to "12/25/76" \n "23:11"
        !          3919:        set format x "%A, %d %b %Y"  # "Saturday, 25 Dec 1976"
        !          3920:        set format x "%r %d"         # "11:11:11 pm 12/25/76"
        !          3921:
        !          3922:  Suppose the text is "98/07/06 05:04:03".  Then
        !          3923:        set format x "%1y/%2m/%3d %01H:%02M:%03S"  # "98/ 7/  6 5:04:003"
        !          3924: 3 function style
        !          3925: ?commands set function style
        !          3926: ?commands show function style
        !          3927: ?set function style
        !          3928: ?show function style
        !          3929: ?function style
        !          3930:  The `set function style` command changes the default plotting style for
        !          3931:  function plots.
        !          3932:
        !          3933:  Syntax:
        !          3934:        set function style <style-choice>
        !          3935:        show function style
        !          3936:
        !          3937:  See `set style` for the choices.  If no choice is given, the choices are
        !          3938:  listed.  `show function style` shows the current default function plotting
        !          3939:  style.
        !          3940: 3 functions
        !          3941: ?commands show functions
        !          3942: ?show functions
        !          3943:  The `show functions` command lists all user-defined functions and their
        !          3944:  definitions.
        !          3945:
        !          3946:  Syntax:
        !          3947:        show functions
        !          3948:
        !          3949:  For information about the definition and usage of functions in `gnuplot`,
        !          3950:  please see `expressions`.
        !          3951: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/spline/spline.html"> Splines as User Defined Functions.</a>
        !          3952: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/airfoil/airfoil.html">Use of functions and complex variables for airfoils </a>
        !          3953: 3 grid
        !          3954: ?commands set grid
        !          3955: ?commands set nogrid
        !          3956: ?commands show grid
        !          3957: ?set grid
        !          3958: ?set nogrid
        !          3959: ?show grid
        !          3960: ?grid
        !          3961: ?nogrid
        !          3962:  The `set grid` command allows grid lines to be drawn on the plot.
        !          3963:
        !          3964:  Syntax:
        !          3965:        set grid {{no}{m}xtics} {{no}{m}ytics} {{no}{m}ztics}
        !          3966:                 {{no}{m}x2tics} {{no}{m}y2tics}
        !          3967:                 {polar {<angle>}}
        !          3968:                 { {linestyle <major_linestyle>}
        !          3969:                   | {linetype | lt <major_linetype>}
        !          3970:                     {linewidth | lw <major_linewidth>}
        !          3971:                   { , {linestyle | ls <minor_linestyle>}
        !          3972:                       | {linetype | lt <minor_linetype>}
        !          3973:                         {linewidth | lw <minor_linewidth>} } }
        !          3974:        set nogrid
        !          3975:        show grid
        !          3976:
        !          3977:  The grid can be enabled and disabled for the major and/or minor tic
        !          3978:  marks on any axis, and the linetype and linewidth can be specified
        !          3979:  for major and minor grid lines, also via a predefined linestyle, as
        !          3980:  far as the active terminal driver supports this.
        !          3981:
        !          3982:  Additionally, a polar grid can be selected for 2-d plots---circles are drawn
        !          3983:  to intersect the selected tics, and radial lines are drawn at definable
        !          3984:  intervals.  (The interval is given in degrees or radians ,depending on the
        !          3985:  `set angles` setting.)  Note that a polar grid is no longer automatically
        !          3986:  generated in polar mode.
        !          3987:
        !          3988:  The pertinent tics must be enabled before `set grid` can draw them; `gnuplot`
        !          3989:  will quietly ignore instructions to draw grid lines at non-existent tics, but
        !          3990:  they will appear if the tics are subsequently enabled.
        !          3991:
        !          3992:  If no linetype is specified for the minor gridlines, the same linetype as the
        !          3993:  major gridlines is used.  The default polar angle is 30 degrees.
        !          3994:
        !          3995:  Z grid lines are drawn on the back of the plot.  This looks better if a
        !          3996:  partial box is drawn around the plot---see `set border`.
        !          3997: 3 hidden3d
        !          3998: ?commands set hidden3d
        !          3999: ?commands set nohidden3d
        !          4000: ?commands show hidden3d
        !          4001: ?set hidden3d
        !          4002: ?set nohidden3d
        !          4003: ?show hidden3d
        !          4004: ?hidden3d
        !          4005: ?nohidden3d
        !          4006:  The `set hidden3d` command enables hidden line removal for surface plotting
        !          4007:  (see `splot`).  Some optional features of the underlying algorithm can also
        !          4008:  be controlled using this command.
        !          4009:
        !          4010:  Syntax:
        !          4011:        set hidden3d {defaults} |
        !          4012:                     { {{offset <offset>} | {nooffset}}
        !          4013:                       {trianglepattern <bitpattern>}
        !          4014:                       {{undefined <level>} | {noundefined}}
        !          4015:                       {{no}altdiagonal}
        !          4016:                       {{no}bentover} }
        !          4017:        set nohidden3d
        !          4018:        show hidden3d
        !          4019:
        !          4020:  In contrast to the usual display in gnuplot, hidden line removal actually
        !          4021:  treats the given function or data grids as real surfaces that can't be seen
        !          4022:  through, so parts behind the surface will be hidden by it.  For this to be
        !          4023:  possible, the surface needs to have 'grid structure' (see `splot datafile`
        !          4024:  about this), and it has to be drawn `with lines` or `with linespoints`.
        !          4025:
        !          4026:  When `hidden3d` is set, both the hidden portion of the surface and possibly
        !          4027:  its contours drawn on the base (see `set contour`) as well as the grid will
        !          4028:  be hidden.  Each surface has its hidden parts removed with respect to itself
        !          4029:  and to other surfaces, if more than one surface is plotted.  Contours drawn
        !          4030:  on the surface (`set contour surface`) don't work.  Labels and arrows are
        !          4031:  always visible and are unaffected.  The key is also never hidden by the
        !          4032:  surface.
        !          4033:
        !          4034:  Functions are evaluated at isoline intersections.  The algorithm interpolates
        !          4035:  linearly between function points or data points when determining the visible
        !          4036:  line segments.  This means that the appearance of a function may be different
        !          4037:  when plotted with `hidden3d` than when plotted with `nohidden3d` because in
        !          4038:  the latter case functions are evaluated at each sample.  Please see `set
        !          4039:  samples` and `set isosamples` for discussion of the difference.
        !          4040:
        !          4041:  The algorithm used to remove the hidden parts of the surfaces has some
        !          4042:  additional features controllable by this command.  Specifying `defaults` will
        !          4043:  set them all to their default settings, as detailed below.  If `defaults` is
        !          4044:  not given, only explicitly specified options will be influenced: all others
        !          4045:  will keep their previous values, so you can turn on/off hidden line removal
        !          4046:  via `set {no}hidden3d`, without modifying the set of options you chose.
        !          4047:
        !          4048:  The first option, `offset`, influences the linestyle used for lines on the
        !          4049:  'back' side.  Normally, they are drawn in a linestyle one index number higher
        !          4050:  than the one used for the front, to make the two sides of the surface
        !          4051:  distinguishable.  You can specify a different line style offset to add
        !          4052:  instead of the default 1, by `offset <offset>`.  Option `nooffset` stands for
        !          4053:  `offset 0`, making the two sides of the surface use the same linestyle.
        !          4054:
        !          4055:  Next comes the option `trianglepattern <bitpattern>`.  <bitpattern> must be
        !          4056:  a number between 0 and 7, interpreted as a bit pattern.  Each bit determines
        !          4057:  the visibility of one edge of the triangles each surface is split up into.
        !          4058:  Bit 0 is for the 'horizontal' edges of the grid, Bit 1 for the 'vertical'
        !          4059:  ones, and Bit 2 for the diagonals that split each cell of the original grid
        !          4060:  into two triangles.  The default pattern is 3, making all horizontal and
        !          4061:  vertical lines visible, but not the diagonals.  You may want to choose 7 to
        !          4062:  see those diagonals as well.
        !          4063:
        !          4064:  The `undefined <level>` option lets you decide what the algorithm is to do
        !          4065:  with data points that are undefined (missing data, or undefined function
        !          4066:  values), or exceed the given x-, y- or z-ranges.  Such points can either be
        !          4067:  plotted nevertheless, or taken out of the input data set.  All surface
        !          4068:  elements touching a point that is taken out will be taken out as well, thus
        !          4069:  creating a hole in the surface.  If <level> = 3, equivalent to option
        !          4070:  `noundefined`, no points will be thrown away at all.  This may produce all
        !          4071:  kinds of problems elsewhere, so you should avoid this.  <level> = 2 will
        !          4072:  throw away undefined points, but keep the out-of-range ones.  <level> = 1,
        !          4073:  the default, will get rid of out-of-range points as well.
        !          4074:
        !          4075:  By specifying `noaltdiagonal`, you can override the default handling of a
        !          4076:  special case can occur if `undefined` is active (i.e. <level> is not 3).
        !          4077:  Each cell of the grid-structured input surface will be divided in two
        !          4078:  triangles along one of its diagonals.  Normally, all these diagonals have
        !          4079:  the same orientation relative to the grid.  If exactly one of the four cell
        !          4080:  corners is excluded by the `undefined` handler, and this is on the usual
        !          4081:  diagonal, both triangles will be excluded.  However if the default setting
        !          4082:  of `altdiagonal` is active, the other diagonal will be chosen for this cell
        !          4083:  instead, minimizing the size of the hole in the surface.
        !          4084:
        !          4085:  The `bentover` option controls what happens to another special case, this
        !          4086:  time in conjunction with the `trianglepattern`.  For rather crumply surfaces,
        !          4087:  it can happen that the two triangles a surface cell is divided into are seen
        !          4088:  from opposite sides (i.e. the original quadrangle is 'bent over'), as
        !          4089:  illustrated in the following ASCII art:
        !          4090:
        !          4091:                                                                C----B
        !          4092:      original quadrangle:  A--B      displayed quadrangle:     |\   |
        !          4093:        ("set view 0,0")    | /|    ("set view 75,75" perhaps)  | \  |
        !          4094:                            |/ |                                |  \ |
        !          4095:                            C--D                                |   \|
        !          4096:                                                                A    D
        !          4097:
        !          4098:  If the diagonal edges of the surface cells aren't generally made visible by
        !          4099:  bit 2 of the <bitpattern> there, the edge CB above wouldn't be drawn at all,
        !          4100:  normally, making the resulting display hard to understand.  Therefore, the
        !          4101:  default option of `bentover` will turn it visible in this case.  If you don't
        !          4102:  want that, you may choose `nobentover` instead.
        !          4103: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/hidden/hidden.html"> Hidden Line Removal Demo</a> and
        !          4104: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/singulr/singulr.html"> Complex Hidden Line Demo. </a>
        !          4105: 3 isosamples
        !          4106: ?commands set isosamples
        !          4107: ?commands show isosamples
        !          4108: ?set isosamples
        !          4109: ?show isosamples
        !          4110: ?isosamples
        !          4111:  The isoline density (grid) for plotting functions as surfaces may be changed
        !          4112:  by the `set isosamples` command.
        !          4113:
        !          4114:  Syntax:
        !          4115:        set isosamples <iso_1> {,<iso_2>}
        !          4116:        show isosamples
        !          4117:
        !          4118:  Each function surface plot will have <iso_1> iso-u lines and <iso_2> iso-v
        !          4119:  lines.  If you only specify <iso_1>, <iso_2> will be set to the same value
        !          4120:  as <iso_1>.  By default, sampling is set to 10 isolines per u or v axis.
        !          4121:  A higher sampling rate will produce more accurate plots, but will take longer.
        !          4122:  These parameters have no effect on data file plotting.
        !          4123:
        !          4124:  An isoline is a curve parameterized by one of the surface parameters while
        !          4125:  the other surface parameter is fixed.  Isolines provide a simple means to
        !          4126:  display a surface.  By fixing the u parameter of surface s(u,v), the iso-u
        !          4127:  lines of the form c(v) = s(u0,v) are produced, and by fixing the v parameter,
        !          4128:  the iso-v lines of the form c(u) = s(u,v0) are produced.
        !          4129:
        !          4130:  When a function surface plot is being done without the removal of hidden
        !          4131:  lines, `set samples`  controls the number of points sampled along each
        !          4132:  isoline;  see `set samples` and `set hidden3d`.  The contour algorithm
        !          4133:  assumes that a function sample occurs at each isoline intersection, so
        !          4134:  change in `samples` as well as `isosamples` may be desired when changing
        !          4135:  the resolution of a function surface/contour.
        !          4136: 3 key
        !          4137: ?commands set key
        !          4138: ?commands set nokey
        !          4139: ?commands show key
        !          4140: ?set key
        !          4141: ?set nokey
        !          4142: ?show key
        !          4143: ?key
        !          4144: ?nokey
        !          4145: ?legend
        !          4146:  The `set key` enables a key (or legend) describing plots on a plot.
        !          4147:
        !          4148:  The contents of the key, i.e., the names given to each plotted data set and
        !          4149:  function and samples of the lines and/or symbols used to represent them, are
        !          4150:  determined by the `title` and `with` options of the {`s`}`plot` command.
        !          4151:  Please see `plot title` and `plot with` for more information.
        !          4152:
        !          4153:  Syntax:
        !          4154:        set key {  left | right | top | bottom | outside | below
        !          4155:                 | <position>}
        !          4156:                {Left | Right} {{no}reverse}
        !          4157:                {samplen <sample_length>} {spacing <vertical_spacing>}
        !          4158:                {width <width_increment>}
        !          4159:                {title "<text>"}
        !          4160:                {{no}box { {linestyle | ls <line_style>}
        !          4161:                           | {linetype | lt <line_type>}
        !          4162:                             {linewidth | lw <line_width>}}}
        !          4163:        set nokey
        !          4164:        show key
        !          4165:
        !          4166:  By default the key is placed in the upper right corner of the graph.  The
        !          4167:  keywords `left`, `right`, `top`, `bottom`, `outside` and `below` may be used
        !          4168:  to place the key in the other corners inside the graph or to the right
        !          4169:  (outside) or below the graph.  They may be given alone or combined.
        !          4170:
        !          4171:  Justification of the labels within the key is controlled by `Left` or `Right`
        !          4172:  (default is `Right`).  The text and sample can be reversed (`reverse`) and a
        !          4173:  box can be drawn around the key (`box {...}`) in a specified `linetype`
        !          4174:  and `linewidth`, or a user-defined `linestyle`. Note that not all
        !          4175:  terminal drivers support linewidth selection, though.
        !          4176:
        !          4177:  The length of the sample line can be controlled by `samplen`.  The sample
        !          4178:  length is computed as the sum of the tic length and <sample_length> times the
        !          4179:  character width.  `samplen` also affects the positions of point samples in
        !          4180:  the key since these are drawn at the midpoint of the sample line, even if it
        !          4181:  is not drawn.  <sample_length> must be an integer.
        !          4182:
        !          4183:  The vertical spacing between lines is controlled by `spacing`.  The spacing
        !          4184:  is set equal to the product of the pointsize, the vertical tic size, and
        !          4185:  <vertical_spacing>.  The program will guarantee that the vertical spacing is
        !          4186:  no smaller than the character height.
        !          4187:
        !          4188:  The <width_increment> is a number of character widths to be added to or
        !          4189:  subtracted from the length of the string.  This is useful only when you are
        !          4190:  putting a box around the key and you are using control characters in the text.
        !          4191:  `gnuplot` simply counts the number of characters in the string when computing
        !          4192:  the box width; this allows you to correct it.
        !          4193:
        !          4194:  A title can be put on the key (`title "<text>"`)---see also `syntax` for the
        !          4195:  distinction between text in single- or double-quotes.  The key title uses the
        !          4196:  same justification as do the plot titles.
        !          4197:
        !          4198:  The defaults for `set key` are `right`, `top`, `Right`, `noreverse`, `samplen
        !          4199:  4`, `spacing 1.25`, `title ""`, and `nobox`.  The default <linetype> is the
        !          4200:  same as that used for the plot borders.  Entering `set key` with no options
        !          4201:  returns the key to its default configuration.
        !          4202:
        !          4203:  The <position> can be a simple x,y,z as in previous versions, but these can
        !          4204:  be preceded by one of four keywords (`first`, `second`, `graph`, `screen`)
        !          4205:  which selects the coordinate system in which the position is specified.  See
        !          4206:  `coordinates` for more details.
        !          4207:
        !          4208:  The key is drawn as a sequence of lines, with one plot described on each
        !          4209:  line.  On the right-hand side (or the left-hand side, if `reverse` is
        !          4210:  selected) of each line is a representation that attempts to mimic the way the
        !          4211:  curve is plotted.  On the other side of each line is the text description
        !          4212:  (the line title), obtained from the `plot` command.  The lines are vertically
        !          4213:  arranged so that an imaginary straight line divides the left- and right-hand
        !          4214:  sides of the key.  It is the coordinates of the top of this line that are
        !          4215:  specified with the `set key` command.  In a `plot`, only the x and y
        !          4216:  coordinates are used to specify the line position.  For a `splot`, x, y and
        !          4217:  z are all used as a 3-d location mapped using the same mapping as the graph
        !          4218:  itself to form the required 2-d screen position of the imaginary line.
        !          4219:
        !          4220:  Some or all of the key may be outside of the graph boundary, although this
        !          4221:  may interfere with other labels and may cause an error on some devices.  If
        !          4222:  you use the keywords `outside` or `below`, `gnuplot` makes space for the keys
        !          4223:  and the graph becomes smaller.  Putting keys outside to the right, they
        !          4224:  occupy as few columns as possible, and putting them below, as many columns as
        !          4225:  possible (depending of the length of the labels), thus stealing as little
        !          4226:  space from the graph as possible.
        !          4227:
        !          4228:  When using the TeX or PostScript drivers, or similar drivers where formatting
        !          4229:  information is embedded in the string, `gnuplot` is unable to calculate
        !          4230:  correctly the width of the string for key positioning.  If the key is to be
        !          4231:  positioned at the left, it may be convenient to use the combination  `set key
        !          4232:  left Left reverse`.  The box and gap in the grid will be the width of the
        !          4233:  literal string.
        !          4234:
        !          4235:  If `splot` is being used to draw contours, the contour labels will be listed
        !          4236:  in the key.  If the alignment of these labels is poor or a different number
        !          4237:  of decimal places is desired, the label format can be specified.  See `set
        !          4238:  clabel` for details.
        !          4239:
        !          4240:  Examples:
        !          4241:
        !          4242:  This places the key at the default location:
        !          4243:        set key
        !          4244:
        !          4245:  This disables the key:
        !          4246:        set nokey
        !          4247:
        !          4248:  This places a key at coordinates 2,3.5,2 in the default (first) coordinate
        !          4249:  system:
        !          4250:        set key 2,3.5,2
        !          4251:
        !          4252:  This places the key below the graph:
        !          4253:        set key below
        !          4254:
        !          4255:  This places the key in the bottom left corner, left-justifies the text,
        !          4256:  gives it a title, and draws a box around it in linetype 3:
        !          4257:        set key left bottom Left title 'Legend' box 3
        !          4258: 3 label
        !          4259: ?commands set label
        !          4260: ?commands set nolabel
        !          4261: ?commands show label
        !          4262: ?set label
        !          4263: ?set nolabel
        !          4264: ?show label
        !          4265: ?label
        !          4266: ?nolabel
        !          4267:  Arbitrary labels can be placed on the plot using the `set label` command.
        !          4268:
        !          4269:  Syntax:
        !          4270:        set label {<tag>} {"<label_text>"} {at <position>}
        !          4271:                  {<justification>} {{no}rotate} {font "<name><,size>"}
        !          4272:        set nolabel {<tag>}
        !          4273:        show label
        !          4274:
        !          4275:  The <position> is specified by either x,y or x,y,z, and may be preceded by
        !          4276:  `first`, `second`, `graph`, or `screen` to select the coordinate system.
        !          4277:  See `coordinates` for details.
        !          4278:
        !          4279:  The tag is an integer that is used to identify the label. If no <tag> is
        !          4280:  given, the lowest unused tag value is assigned automatically.  The tag can be
        !          4281:  used to delete or modify a specific label.  To change any attribute of an
        !          4282:  existing label, use the `set label` command with the appropriate tag, and
        !          4283:  specify the parts of the label to be changed.
        !          4284:
        !          4285:  By default, the text is placed flush left against the point x,y,z.  To adjust
        !          4286:  the way the label is positioned with respect to the point x,y,z, add the
        !          4287:  parameter <justification>, which may be `left`, `right` or `center`,
        !          4288:  indicating that the point is to be at the left, right or center of the text.
        !          4289:  Labels outside the plotted boundaries are permitted but may interfere with
        !          4290:  axis labels or other text.
        !          4291:
        !          4292:  If `rotate` is given, the label is written vertically (if the terminal can do
        !          4293:  so, of course).
        !          4294:
        !          4295:  If one (or more) axis is timeseries, the appropriate coordinate should be
        !          4296:  given as a quoted time string according to the `timefmt` format string.  See
        !          4297:  `set xdata` and `set timefmt`.
        !          4298:
        !          4299:  The EEPIC, Imagen, LaTeX, and TPIC drivers allow \\ in a string to specify
        !          4300:  a newline.
        !          4301:
        !          4302:  Examples:
        !          4303:
        !          4304:  To set a label at (1,2) to "y=x", use:
        !          4305:        set label "y=x" at 1,2
        !          4306:
        !          4307:  To set a Sigma of size 24, from the Symbol font set, at the center of
        !          4308:  the graph, use:
        !          4309:        set label "S" at graph 0.5,0.5 center font "Symbol,24"
        !          4310:
        !          4311:  To set a label "y=x^2" with the right of the text at (2,3,4), and tag the
        !          4312:  label as number 3, use:
        !          4313:        set label 3 "y=x^2" at 2,3,4 right
        !          4314:
        !          4315:  To change the preceding label to center justification, use:
        !          4316:        set label 3 center
        !          4317:
        !          4318:  To delete label number 2, use:
        !          4319:        set nolabel 2
        !          4320:
        !          4321:  To delete all labels, use:
        !          4322:        set nolabel
        !          4323:
        !          4324:  To show all labels (in tag order), use:
        !          4325:        show label
        !          4326:
        !          4327:  To set a label on a graph with a timeseries on the x axis, use, for example:
        !          4328:        set timefmt "%d/%m/%y,%H:%M"
        !          4329:        set label "Harvest" at "25/8/93",1
        !          4330: 3 linestyle
        !          4331: ?commands set linestyle
        !          4332: ?commands set nolinestyle
        !          4333: ?commands show linestyle
        !          4334: ?set linestyle
        !          4335: ?set nolinestyle
        !          4336: ?show linestyle
        !          4337: ?linestyle
        !          4338:  Each terminal has a default set of line and point types, which can be seen
        !          4339:  by using the command `test`.  `set linestyle` defines a set of line types
        !          4340:  and widths and point types and sizes so that you can refer to them later by
        !          4341:  an index instead of repeating all the information at each invocation.
        !          4342:
        !          4343:  Syntax:
        !          4344:        set linestyle <index> {linetype | lt <line_type>}
        !          4345:                              {linewidth | lw <line_width>}
        !          4346:                              {pointtype | pt <point_type>}
        !          4347:                              {pointsize | ps <point_size>}
        !          4348:        set nolinestyle
        !          4349:        show linestyle
        !          4350:
        !          4351:  The line and point types are taken from the default types for the terminal
        !          4352:  currently in use.  The line width and point size are multipliers for the
        !          4353:  default width and size (but note that <point_size> here is unaffected by
        !          4354:  the multiplier given on 'set pointsize').
        !          4355:
        !          4356:  The defaults for the line and point types is the index.  The defaults for
        !          4357:  the width and size are both unity.
        !          4358:
        !          4359:  Linestyles created by this mechanism do not replace the default styles;
        !          4360:  both may be used.
        !          4361:
        !          4362:  Not all terminals support the `linewidth` and `pointsize` features; if
        !          4363:  not supported, the option will be ignored.
        !          4364:
        !          4365:  Note that this feature is not completely implemented; linestyles defined by
        !          4366:  this mechanism may be used with 'plot', 'splot', 'replot', and 'set arrow',
        !          4367:  but not by other commands that allow the default index to be used, such as
        !          4368:  'set grid'.
        !          4369:
        !          4370:  Example:
        !          4371:  Suppose that the default lines for indices 1, 2, and 3 are red, green, and
        !          4372:  blue, respectively, and the default point shapes for the same indices are a
        !          4373:  square, a cross, and a triangle, respectively.  Then
        !          4374:
        !          4375:        set linestyle 1 lt 2 lw 2 pt 3 ps 0.5
        !          4376:
        !          4377:  defines a new linestyle that is green and twice the default width and a new
        !          4378:  pointstyle that is a half-sized triangle.  The commands
        !          4379:
        !          4380:        set function style lines
        !          4381:        plot f(x) lt 3, g(x) ls 1
        !          4382:
        !          4383:  will create a plot of f(x) using the default blue line and a plot of g(x)
        !          4384:  using the user-defined wide green line.  Similarly the commands
        !          4385:
        !          4386:        set function style linespoints
        !          4387:        plot p(x) lt 1 pt 3, q(x) ls 1
        !          4388:
        !          4389:  will create a plot of f(x) using the default triangles connected by a red
        !          4390:  line and q(x) using small triangles connected by a green line.
        !          4391: 3 lmargin
        !          4392: ?commands set lmargin
        !          4393: ?set lmargin
        !          4394: ?lmargin
        !          4395:  The command `set lmargin` sets the size of the left margin.  Please see
        !          4396:  `set margin` for details.
        !          4397: 3 locale
        !          4398: ?commands set locale
        !          4399: ?commands show logscale
        !          4400: ?set locale
        !          4401: ?show logscale
        !          4402: ?locale
        !          4403:  The `locale` setting determines the language with which `{x,y,z}{d,m}tics`
        !          4404:  will write the days and months.
        !          4405:
        !          4406:  Syntax:
        !          4407:        set locale {"<locale>"}
        !          4408:
        !          4409:  <locale> may be any language designation acceptable to your installation.
        !          4410:  See your system documentation for the available options.  The default value
        !          4411:  is determined from the LANG environment variable.
        !          4412: 3 logscale
        !          4413: ?commands set logscale
        !          4414: ?commands set nologscale
        !          4415: ?commands show logscale
        !          4416: ?set logscale
        !          4417: ?set nologscale
        !          4418: ?show logscale
        !          4419: ?logscale
        !          4420: ?nologscale
        !          4421:  Log scaling may be set on the x, y, z, x2 and/or y2 axes.
        !          4422:
        !          4423:  Syntax:
        !          4424:        set logscale <axes> <base>
        !          4425:        set nologscale <axes>
        !          4426:        show logscale
        !          4427:
        !          4428:  where <axes> may be any combinations of `x`, `y`, and `z`, in any order, or
        !          4429:  `x2` or `y2` and where <base> is the base of the log scaling.  If <base> is
        !          4430:  not given, then 10 is assumed.  If <axes> is not given, then all axes are
        !          4431:  assumed.  `set nologscale` turns off log scaling for the specified axes.
        !          4432:
        !          4433:  Examples:
        !          4434:
        !          4435:  To enable log scaling in both x and z axes:
        !          4436:        set logscale xz
        !          4437:
        !          4438:  To enable scaling log base 2 of the y axis:
        !          4439:        set logscale y 2
        !          4440:
        !          4441:  To disable z axis log scaling:
        !          4442:        set nologscale z
        !          4443: 3 mapping
        !          4444: ?commands set mapping
        !          4445: ?commands show mapping
        !          4446: ?set mapping
        !          4447: ?show mapping
        !          4448: ?mapping
        !          4449:  If data are provided to `splot` in spherical or cylindrical coordinates,
        !          4450:  the `set mapping` command should be used to instruct `gnuplot` how to
        !          4451:  interpret them.
        !          4452:
        !          4453:  Syntax:
        !          4454:        set mapping {cartesian | spherical | cylindrical}
        !          4455:
        !          4456:  A cartesian coordinate system is used by default.
        !          4457:
        !          4458:  For a spherical coordinate system, the data occupy two or three columns (or
        !          4459:  `using` entries).  The first two are interpreted as the polar and azimuthal
        !          4460:  angles theta and phi (in the units specified by `set angles`).  The radius r
        !          4461:  is taken from the third column if there is one, or is set to unity if there
        !          4462:  is no third column.  The mapping is:
        !          4463:
        !          4464:        x = r * cos(theta) * cos(phi)
        !          4465:        y = r * sin(theta) * cos(phi)
        !          4466:        z = r * sin(phi)
        !          4467:
        !          4468:  Note that this is a "geographic" spherical system, rather than a "polar" one.
        !          4469:
        !          4470:  For a cylindrical coordinate system, the data again occupy two or three
        !          4471:  columns.  The first two are interpreted as theta (in the units specified by
        !          4472:  `set angles`) and z.  The radius is either taken from the third column or set
        !          4473:  to unity, as in the spherical case.  The mapping is:
        !          4474:
        !          4475:        x = r * cos(theta)
        !          4476:        y = r * sin(theta)
        !          4477:        z = z
        !          4478:
        !          4479:  The effects of `mapping` can be duplicated with the `using` filter on the
        !          4480:  `splot` command, but `mapping` may be more convenient if many data files are
        !          4481:  to be processed.  However even if `mapping` is used, `using` may still be
        !          4482:  necessary if the data in the file are not in the required order.
        !          4483:
        !          4484:  `mapping` has no effect on `plot`.
        !          4485: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/world/world.html">Mapping Demos.</a>
        !          4486: 3 margin
        !          4487: ?commands set margin
        !          4488: ?commands show margin
        !          4489: ?set margin
        !          4490: ?show margin
        !          4491: ?margin
        !          4492:  Normally the margins of a plot are automatically calculated based on tics
        !          4493:  and axis labels (and the size of the graph correspondingly adjusted.)  These
        !          4494:  computed values can be overridden by the `set margin` commands.  `show margin`
        !          4495:  shows the current settings.
        !          4496:
        !          4497:  Syntax:
        !          4498:        set bmargin {<margin>}
        !          4499:        set lmargin {<margin>}
        !          4500:        set rmargin {<margin>}
        !          4501:        set tmargin {<margin>}
        !          4502:        show margin
        !          4503:
        !          4504:  The units of <margin> are character heights or widths, as appropriate.  A
        !          4505:  positive value defines the absolute size of the margin.  A negative value
        !          4506:  (or none) causes `gnuplot` to revert to the computed value.
        !          4507: 3 missing
        !          4508: ?commands set missing
        !          4509: ?set missing
        !          4510: ?missing
        !          4511:  The `set missing` command allows you to tell `gnuplot` what character is
        !          4512:  used in a data file to denote missing data.
        !          4513:
        !          4514:  Syntax:
        !          4515:        set missing {"<character>"}
        !          4516:        show missing
        !          4517:
        !          4518:  Example:
        !          4519:        set missing "?"
        !          4520:
        !          4521:  would mean that, when plotting a file containing
        !          4522:
        !          4523:           1 1
        !          4524:           2 ?
        !          4525:           3 2
        !          4526:
        !          4527:  the middle line would be ignored.
        !          4528:
        !          4529:  There is no default character for `missing`.
        !          4530: 3 multiplot
        !          4531: ?commands set multiplot
        !          4532: ?commands set nomultiplot
        !          4533: ?set multiplot
        !          4534: ?set nomultiplot
        !          4535: ?multiplot
        !          4536: ?nomultiplot
        !          4537:  The command `set multiplot` places `gnuplot` in the multiplot mode, in which
        !          4538:  several plots are placed on the same page, window, or screen.
        !          4539:
        !          4540:  Syntax:
        !          4541:        set multiplot
        !          4542:        set nomultiplot
        !          4543:
        !          4544:  For some terminals, no plot is displayed until the command `set nomultiplot`
        !          4545:  is given, which causes the entire page to be drawn and then returns `gnuplot`
        !          4546:  to its normal single-plot mode.  For other terminals, each separate `plot`
        !          4547:  command produces a plot, but the screen may not be cleared between plots.
        !          4548:
        !          4549:  Any labels or arrows that have been defined will be drawn for each plot
        !          4550:  according to the current size and origin (unless their coordinates are
        !          4551:  defined in the `screen` system).  Just about everything else that can be
        !          4552:  `set` is applied to each plot, too.  If you want something to appear only
        !          4553:  once on the page, for instance a single time stamp, you'll need to put a `set
        !          4554:  time`/`set notime` pair around one of the `plot`, `splot` or `replot`
        !          4555:  commands within the `set multiplot`/`set nomultiplot` block.
        !          4556:
        !          4557:  The commands `set origin` and `set size` must be used to correctly position
        !          4558:  each plot; see `set origin` and `set size` for details of their usage.
        !          4559:
        !          4560:  Example:
        !          4561:        set size 0.7,0.7
        !          4562:        set origin 0.1,0.1
        !          4563:        set multiplot
        !          4564:        set size 0.4,0.4
        !          4565:        set origin 0.1,0.1
        !          4566:        plot sin(x)
        !          4567:        set size 0.2,0.2
        !          4568:        set origin 0.5,0.5
        !          4569:        plot cos(x)
        !          4570:        set nomultiplot
        !          4571:
        !          4572:  displays a plot of cos(x) stacked above a plot of sin(x).  Note the initial
        !          4573:  `set size` and `set origin`.  While these are not always required, their
        !          4574:  inclusion is recommended.  Some terminal drivers require that bounding box
        !          4575:  information be available before any plots can be made, and the form given
        !          4576:  above guarantees that the bounding box will include the entire plot array
        !          4577:  rather than just the bounding box of the first plot.
        !          4578:
        !          4579:  `set size` and `set origin` refer to the entire plotting area used for each
        !          4580:  plot.  If you want to have the axes themselves line up, you can guarantee
        !          4581:  that the margins are the same size with the `set margin` commands.  See
        !          4582:  `set margin` for their use.  Note that the margin settings are absolute,
        !          4583:  in character units, so the appearance of the graph in the remaining space
        !          4584:  will depend on the screen size of the display device, e.g., perhaps quite
        !          4585:  different on a video display and a printer.
        !          4586: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/multiplot/multiplt.html"> See demo. </a>
        !          4587: 3 mx2tics
        !          4588: ?commands set mx2tics
        !          4589: ?commands set nomx2tics
        !          4590: ?commands show mx2tics
        !          4591: ?set mx2tics
        !          4592: ?set nomx2tics
        !          4593: ?show mx2tics
        !          4594: ?mx2tics
        !          4595: ?nomx2tics
        !          4596:  Minor tic marks along the x2 (top) axis are controlled by `set mx2tics`.
        !          4597:  Please see `set mxtics`.
        !          4598: 3 mxtics
        !          4599: ?commands set mxtics
        !          4600: ?commands set nomxtics
        !          4601: ?commands show mxtics
        !          4602: ?set mxtics
        !          4603: ?set nomxtics
        !          4604: ?show mxtics
        !          4605: ?mxtics
        !          4606: ?nomxtics
        !          4607:  Minor tic marks along the x axis are controlled by `set mxtics`.  They can be
        !          4608:  turned off with `set nomxtics`.  Similar commands control minor tics along
        !          4609:  the other axes.
        !          4610:
        !          4611:  Syntax:
        !          4612:        set mxtics {<freq> | default}
        !          4613:        set nomxtics
        !          4614:        show mxtics
        !          4615:
        !          4616:  The same syntax applies to `mytics`, `mztics`, `mx2tics` and `my2tics`.
        !          4617:
        !          4618:  <freq> is the number of sub-intervals (NOT the number of minor tics) between
        !          4619:  major tics (ten is the default for a linear axis, so there are nine minor
        !          4620:  tics between major tics). Selecting `default` will return the number of minor
        !          4621:  ticks to its default value.
        !          4622:
        !          4623:  If the axis is logarithmic, the number of sub-intervals will be set to a
        !          4624:  reasonable number by default (based upon the length of a decade).  This will
        !          4625:  be overridden if <freq> is given.  However the usual minor tics (2, 3, ...,
        !          4626:  8, 9 between 1 and 10, for example) are obtained by setting <freq> to 10,
        !          4627:  even though there are but nine sub-intervals.
        !          4628:
        !          4629:  Minor tics can be used only with uniformly spaced major tics.  Since major
        !          4630:  tics can be placed arbitrarily by `set {x|x2|y|y2|z}tics`, minor tics cannot
        !          4631:  be used if major tics are explicitly `set`.
        !          4632:
        !          4633:  By default, minor tics are off for linear axes and on for logarithmic axes.
        !          4634:  They inherit the settings for `axis|border` and `{no}mirror` specified for
        !          4635:  the major tics.  Please see `set xtics` for information about these.
        !          4636: 3 my2tics
        !          4637: ?commands set my2tics
        !          4638: ?commands set nomy2tics
        !          4639: ?commands show my2tics
        !          4640: ?set my2tics
        !          4641: ?set nomy2tics
        !          4642: ?show my2tics
        !          4643: ?my2tics
        !          4644: ?nomy2tics
        !          4645:  Minor tic marks along the y2 (right-hand) axis are controlled by `set
        !          4646:  my2tics`.  Please see `set mxtics`.
        !          4647: 3 mytics
        !          4648: ?commands set mytics
        !          4649: ?commands set nomytics
        !          4650: ?commands show mytics
        !          4651: ?set mytics
        !          4652: ?set nomytics
        !          4653: ?show mytics
        !          4654: ?mytics
        !          4655: ?nomytics
        !          4656:  Minor tic marks along the y axis are controlled by `set mytics`.  Please
        !          4657:  see `set mxtics`.
        !          4658: 3 mztics
        !          4659: ?commands set mztics
        !          4660: ?commands set nomztics
        !          4661: ?commands show mztics
        !          4662: ?set mztics
        !          4663: ?set nomztics
        !          4664: ?show mztics
        !          4665: ?mztics
        !          4666: ?nomztics
        !          4667:  Minor tic marks along the z axis are controlled by `set mztics`.  Please
        !          4668:  see `set mxtics`.
        !          4669: 3 offsets
        !          4670: ?commands set offsets
        !          4671: ?commands set nooffsets
        !          4672: ?commands show offsets
        !          4673: ?set offsets
        !          4674: ?set nooffsets
        !          4675: ?show offsets
        !          4676: ?offsets
        !          4677: ?nooffsets
        !          4678:  Offsets provide a mechanism to put a boundary around the data inside of an
        !          4679:  autoscaled graph.
        !          4680:
        !          4681:  Syntax:
        !          4682:        set offsets <left>, <right>, <top>, <bottom>
        !          4683:        set nooffsets
        !          4684:        show offsets
        !          4685:
        !          4686:  Each offset may be a constant or an expression.  Each defaults to 0.  Left
        !          4687:  and right offsets are given in units of the x axis, top and bottom offsets in
        !          4688:  units of the y axis.  A positive offset expands the graph in the specified
        !          4689:  direction, e.g., a positive bottom offset makes ymin more negative.  Negative
        !          4690:  offsets, while permitted, can have unexpected interactions with autoscaling
        !          4691:  and clipping.
        !          4692:
        !          4693:  Offsets are ignored in `splot`s.
        !          4694:
        !          4695:  Example:
        !          4696:        set offsets 0, 0, 2, 2
        !          4697:        plot sin(x)
        !          4698:
        !          4699:  This graph of sin(x) will have a y range [-3:3] because the function
        !          4700:  will be autoscaled to [-1:1] and the vertical offsets are each two.
        !          4701: 3 origin
        !          4702: ?commands set origin
        !          4703: ?commands show origin
        !          4704: ?set origin
        !          4705: ?show origin
        !          4706: ?origin
        !          4707:  The `set origin` command is used to specify the origin of a plotting surface
        !          4708:  (i.e., the graph and its margins) on the screen.  The coordinates are given
        !          4709:  in the `screen` coordinate system (see `coordinates` for information about
        !          4710:  this system).
        !          4711:
        !          4712:  Syntax:
        !          4713:        set origin <x-origin>,<y-origin>
        !          4714: 3 output
        !          4715: ?commands set output
        !          4716: ?commands show output
        !          4717: ?set output
        !          4718: ?show output
        !          4719: ?output
        !          4720:  By default, screens are displayed to the standard output. The `set output`
        !          4721:  command redirects the display to the specified file or device.
        !          4722:
        !          4723:  Syntax:
        !          4724:        set output {"<filename>"}
        !          4725:        show output
        !          4726:
        !          4727:  The filename must be enclosed in quotes.  If the filename is omitted, any
        !          4728:  output file opened by a previous invocation of `set output` will be closed
        !          4729:  and new output will be sent to STDOUT.  (If you give the command `set output
        !          4730:  "STDOUT"`, your output may be sent to a file named "STDOUT"!  ["May be", not
        !          4731:  "will be", because some terminals, like `x11`, ignore `set output`.])
        !          4732:
        !          4733:  MSDOS users should note that the \ character has special significance in
        !          4734:  double-quoted strings, so single-quotes should be used for filenames in
        !          4735:  different directories.
        !          4736:
        !          4737:  When both `set terminal` and `set output` are used together, it is safest to
        !          4738:  give `set terminal` first, because some terminals set a flag which is needed
        !          4739:  in some operating systems.  This would be the case, for example, if the
        !          4740:  operating system needs to know whether or not a file is to be formatted in
        !          4741:  order to open it properly.
        !          4742:
        !          4743:  On machines with popen functions (Unix), output can be piped through a shell
        !          4744:  command if the first non-whitespace character of the filename is '|'.
        !          4745:  For instance,
        !          4746:
        !          4747:        set output "|lpr -Plaser filename"
        !          4748:        set output "|lp -dlaser filename"
        !          4749:
        !          4750:  On MSDOS machines, `set output "PRN"` will direct the output to the default
        !          4751:  printer.  On VMS, output can be sent directly to any spooled device.  It is
        !          4752:  also possible to send the output to DECnet transparent tasks, which allows
        !          4753:  some flexibility.
        !          4754: 3 parametric
        !          4755: ?commands set parametric
        !          4756: ?commands set noparametric
        !          4757: ?commands show parametric
        !          4758: ?set parametric
        !          4759: ?set noparametric
        !          4760: ?show parametric
        !          4761: ?parametric
        !          4762: ?noparametric
        !          4763:  The `set parametric` command changes the meaning of `plot` (`splot`) from
        !          4764:  normal functions to parametric functions.  The command `set noparametric`
        !          4765:  restores the plotting style to normal, single-valued expression plotting.
        !          4766:
        !          4767:  Syntax:
        !          4768:        set parametric
        !          4769:        set noparametric
        !          4770:        show parametric
        !          4771:
        !          4772:  For 2-d plotting, a parametric function is determined by a pair of parametric
        !          4773:  functions operating on a parameter.  An example of a 2-d parametric function
        !          4774:  would be `plot sin(t),cos(t)`, which draws a circle (if the aspect ratio is
        !          4775:  set correctly---see `set size`).  `gnuplot` will display an error message if
        !          4776:  both functions are not provided for a parametric `plot`.
        !          4777:
        !          4778:  For 3-d plotting, the surface is described as x=f(u,v), y=g(u,v), z=h(u,v).
        !          4779:  Therefore a triplet of functions is required.  An example of a 3-d parametric
        !          4780:  function would be `cos(u)*cos(v),cos(u)*sin(v),sin(u)`, which draws a sphere.
        !          4781:  `gnuplot` will display an error message if all three functions are not
        !          4782:  provided for a parametric `splot`.
        !          4783:
        !          4784:  The total set of possible plots is a superset of the simple f(x) style plots,
        !          4785:  since the two functions can describe the x and y values to be computed
        !          4786:  separately.  In fact, plots of the type t,f(t) are equivalent to those
        !          4787:  produced with f(x) because the x values are computed using the identity
        !          4788:  function.  Similarly, 3-d plots of the type u,v,f(u,v) are equivalent to
        !          4789:  f(x,y).
        !          4790:
        !          4791:  Note that the order the parametric functions are specified is xfunction,
        !          4792:  yfunction (and zfunction) and that each operates over the common parametric
        !          4793:  domain.
        !          4794:
        !          4795:  Also, the `set parametric` function implies a new range of values.  Whereas
        !          4796:  the normal f(x) and f(x,y) style plotting assume an xrange and yrange (and
        !          4797:  zrange), the parametric mode additionally specifies a trange, urange, and
        !          4798:  vrange.  These ranges may be set directly with `set trange`, `set urange`,
        !          4799:  and `set vrange`, or by specifying the range on the `plot` or `splot`
        !          4800:  commands.  Currently the default range for these parametric variables is
        !          4801:  [-5:5].  Setting the ranges to something more meaningful is expected.
        !          4802: 3 pointsize
        !          4803: ?commands set pointsize
        !          4804: ?commands show pointsize
        !          4805: ?set pointsize
        !          4806: ?show pointsize
        !          4807: ?pointsize
        !          4808:  The `set pointsize` command scales the size of the points used in plots.
        !          4809:
        !          4810:  Syntax:
        !          4811:        set pointsize <multiplier>
        !          4812:        show pointsize
        !          4813:
        !          4814:  The default is a multiplier of 1.0.  Larger pointsizes may be useful to
        !          4815:  make points more visible in bitmapped graphics.
        !          4816:
        !          4817:  The pointsize of a single plot may be changed on the `plot` command.  See
        !          4818:  `plot with` for details.
        !          4819:
        !          4820:  Please note that the pointsize setting is not supported by all terminal
        !          4821:  types.
        !          4822: 3 polar
        !          4823: ?commands set polar
        !          4824: ?commands set nopolar
        !          4825: ?commands show polar
        !          4826: ?set polar
        !          4827: ?set nopolar
        !          4828: ?show polar
        !          4829: ?polar
        !          4830: ?nopolar
        !          4831:  The `set polar` command changes the meaning of the plot from rectangular
        !          4832:  coordinates to polar coordinates.
        !          4833:
        !          4834:  Syntax:
        !          4835:        set polar
        !          4836:        set nopolar
        !          4837:        show polar
        !          4838:
        !          4839:  There have been changes made to polar mode in version 3.7, so that scripts
        !          4840:  for `gnuplot` versions 3.5 and earlier will require modification.  The main
        !          4841:  change is that the dummy variable t is used for the angle so that the x and
        !          4842:  y ranges can be controlled independently.  Other changes are:
        !          4843:  1) tics are no longer put along the zero axes automatically
        !          4844:  ---use `set xtics axis nomirror`; `set ytics axis nomirror`;
        !          4845:  2) the grid, if selected, is not automatically polar
        !          4846:  ---use `set grid polar`;
        !          4847:  3) the grid is not labelled with angles
        !          4848:  ---use `set label` as necessary.
        !          4849:
        !          4850:  In polar coordinates, the dummy variable (t) is an angle.  The default range
        !          4851:  of t is [0:2*pi], or, if degree units have been selected, to [0:360] (see
        !          4852:  `set angles`).
        !          4853:
        !          4854:  The command `set nopolar` changes the meaning of the plot back to the default
        !          4855:  rectangular coordinate system.
        !          4856:
        !          4857:  The `set polar` command is not supported for `splot`s.  See the `set mapping`
        !          4858:  command for similar functionality for `splot`s.
        !          4859:
        !          4860:  While in polar coordinates the meaning of an expression in t is really
        !          4861:  r = f(t), where t is an angle of rotation.  The trange controls the domain
        !          4862:  (the angle) of the function, and the x and y ranges control the range of the
        !          4863:  graph in the x and y directions.  Each of these ranges, as well as the
        !          4864:  rrange, may be autoscaled or set explicitly.  See `set xrange` for details
        !          4865:  of all the `set range` commands.
        !          4866:
        !          4867:  Example:
        !          4868:        set polar
        !          4869:        plot t*sin(t)
        !          4870:        plot [-2*pi:2*pi] [-3:3] [-3:3] t*sin(t)
        !          4871:
        !          4872:  The first `plot` uses the default polar angular domain of 0 to 2*pi.  The
        !          4873:  radius and the size of the graph are scaled automatically.  The second `plot`
        !          4874:  expands the domain, and restricts the size of the graph to [-3:3] in both
        !          4875:  directions.
        !          4876:
        !          4877:  You may want to `set size square` to have `gnuplot` try to make the aspect
        !          4878:  ratio equal to unity, so that circles look circular.
        !          4879: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/polar/polar.html">Polar demos </a>
        !          4880: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/poldat/poldat.html">Polar Data Plot. </a>
        !          4881: 3 rmargin
        !          4882: ?commands set rmargin
        !          4883: ?set rmargin
        !          4884: ?rmargin
        !          4885:  The command `set rmargin` sets the size of the right margin.  Please see
        !          4886:  `set margin` for details.
        !          4887: 3 rrange
        !          4888: ?commands set rrange
        !          4889: ?commands show rrange
        !          4890: ?set rrange
        !          4891: ?show rrange
        !          4892: ?rrange
        !          4893:  The `set rrange` command sets the range of the radial coordinate for a
        !          4894:  graph in polar mode.  Please see `set xrange` for details.
        !          4895: 3 samples
        !          4896: ?commands set samples
        !          4897: ?commands show samples
        !          4898: ?set samples
        !          4899: ?show samples
        !          4900: ?samples
        !          4901:  The sampling rate of functions, or for interpolating data, may be changed
        !          4902:  by the `set samples` command.
        !          4903:
        !          4904:  Syntax:
        !          4905:        set samples <samples_1> {,<samples_2>}
        !          4906:        show samples
        !          4907:
        !          4908:  By default, sampling is set to 100 points.  A higher sampling rate will
        !          4909:  produce more accurate plots, but will take longer.  This parameter has no
        !          4910:  effect on data file plotting unless one of the interpolation/approximation
        !          4911:  options is used.  See `plot smooth` re 2-d data and `set cntrparam` and
        !          4912:  `set dgrid3d` re 3-d data.
        !          4913:
        !          4914:  When a 2-d graph is being done, only the value of <samples_1> is relevant.
        !          4915:
        !          4916:  When a surface plot is being done without the removal of hidden lines, the
        !          4917:  value of samples specifies the number of samples that are to be evaluated for
        !          4918:  the isolines.  Each iso-v line will have <sample_1> samples and each iso-u
        !          4919:  line will have <sample_2> samples.  If you only specify <samples_1>,
        !          4920:  <samples_2> will be set to the same value as <samples_1>.  See also `set
        !          4921:  isosamples`.
        !          4922: 3 size
        !          4923: ?commands set size
        !          4924: ?commands show size
        !          4925: ?set size
        !          4926: ?show size
        !          4927: ?size
        !          4928:  The `set size` command scales the displayed size of the plot.
        !          4929:
        !          4930:  Syntax:
        !          4931:        set size {{no}square | ratio <r> | noratio} {<xscale>,<yscale>}
        !          4932:        show size
        !          4933:
        !          4934:  The <xscale> and <yscale> values are the scaling factors for the size of the
        !          4935:  plot, which includes the graph and the margins.
        !          4936:
        !          4937:  `ratio` causes `gnuplot` to try to create a graph with an aspect ratio of <r>
        !          4938:  (the ratio of the y-axis length to the x-axis length) within the portion of
        !          4939:  the plot specified by <xscale> and <yscale>.
        !          4940:
        !          4941:  The meaning of a negative value for <r> is different.  If <r>=-1, gnuplot
        !          4942:  tries to set the scales so that the unit has the same length on both the x
        !          4943:  and y axes (suitable for geographical data, for instance).  If <r>=-2, the
        !          4944:  unit on y has twice the length of the unit on x, and so on.
        !          4945:
        !          4946:  The success of `gnuplot` in producing the requested aspect ratio depends on
        !          4947:  the terminal selected.  The graph area will be the largest rectangle of
        !          4948:  aspect ratio <r> that will fit into the specified portion of the output
        !          4949:  (leaving adequate margins, of course).
        !          4950:
        !          4951:  `square` is a synonym for `ratio 1`.
        !          4952:
        !          4953:  Both `noratio` and `nosquare` return the graph to the default aspect ratio
        !          4954:  of the terminal, but do not return <xscale> or <yscale> to their default
        !          4955:  values (1.0).
        !          4956:
        !          4957:  `ratio` and `square` have no effect on 3-d plots.
        !          4958:
        !          4959:  `set size` is relative to the default size, which differs from terminal to
        !          4960:  terminal.  Since `gnuplot` fills as much of the available plotting area as
        !          4961:  possible by default, it is safer to use `set size` to decrease the size of
        !          4962:  a plot than to increase it.  See `set terminal` for the default sizes.
        !          4963:
        !          4964:  On some terminals, changing the size of the plot will result in text being
        !          4965:  misplaced.
        !          4966:
        !          4967:  Examples:
        !          4968:
        !          4969:  To set the size to normal size use:
        !          4970:        set size 1,1
        !          4971:
        !          4972:  To make the graph half size and square use:
        !          4973:        set size square 0.5,0.5
        !          4974:
        !          4975:  To make the graph twice as high as wide use:
        !          4976:        set size ratio 2
        !          4977:
        !          4978: ^<a href="http://www.nas.nasa.gov/~woo/gnuplot/airfoil/airfoil.html"> See demo. </a>
        !          4979: 3 style
        !          4980: ?commands set function style
        !          4981: ?commands show function style
        !          4982: ?commands set data style
        !          4983: ?commands show data style
        !          4984: ?set function style
        !          4985: ?show function style
        !          4986: ?set data style
        !          4987: ?show data style
        !          4988: ?set style
        !          4989: ?show style
        !          4990:  Default styles are chosen with the `set function style` and `set data style`
        !          4991:  commands.  See `plot with` for information about how to override the default
        !          4992:  plotting style for individual functions and data sets.
        !          4993:
        !          4994:  Syntax:
        !          4995:        set function style <style>
        !          4996:        set data style <style>
        !          4997:        show function style
        !          4998:        show data style
        !          4999:
        !          5000:  The types used for all line and point styles (i.e., solid, dash-dot, color,
        !          5001:  etc. for lines; circles, squares, crosses, etc. for points) will be either
        !          5002:  those specified on the `plot` or `splot` command or will be chosen
        !          5003:  sequentially from the types available to the terminal in use.  Use the
        !          5004:  command `test` to see what is available.
        !          5005:
        !          5006:  None of the styles requiring more than two columns of information (e.g.,
        !          5007:  `errorbars`) can be used with `splot`s or function `plot`s.  Neither `boxes`
        !          5008:  nor any of the `steps` styles can be used with `splot`s.  If an inappropriate
        !          5009:  style is specified, it will be changed to `points`.
        !          5010:
        !          5011:  For 2-d data with more than two columns, `gnuplot` is picky about the allowed
        !          5012:  `errorbar` styles.  The `using` option on the `plot` command can be used to
        !          5013:  set up the correct columns for the style you want.  (In this discussion,
        !          5014:  "column" will be used to refer both to a column in the data file and an entry
        !          5015:  in the `using` list.)
        !          5016:
        !          5017:  For three columns, only `xerrorbars`, `yerrorbars` (or `errorbars`), `boxes`,
        !          5018:  and `boxerrorbars` are allowed.  If another plot style is used, the style
        !          5019:  will be changed to `yerrorbars`.  The `boxerrorbars` style will calculate the
        !          5020:  boxwidth automatically.
        !          5021:
        !          5022:  For four columns, only `xerrorbars`, `yerrorbars` (or `errorbars`),
        !          5023:  `xyerrorbars`, `boxxyerrorbars`, and `boxerrorbars` are allowed.  An illegal
        !          5024:  style will be changed to `yerrorbars`.
        !          5025:
        !          5026:  Five-column data allow only the `boxerrorbars`, `financebars`, and
        !          5027:  `candlesticks` styles.  (The last two of these are primarily used for plots
        !          5028:  of financial prices.)  An illegal style will be changed to `boxerrorbars`
        !          5029:  before plotting.
        !          5030:
        !          5031:  Six- and seven-column data only allow the `xyerrorbars` and `boxxyerrorbars`
        !          5032:  styles.  Illegal styles will be changed to `xyerrorbars` before plotting.
        !          5033:
        !          5034:  For more information about error bars, please see `plot errorbars`.
        !          5035: 4 boxerrorbars
        !          5036: ?commands set style boxerrorbars
        !          5037: ?set style boxerrorbars
        !          5038: ?style boxerrorbars
        !          5039: ?boxerrorbars
        !          5040:  The `boxerrorbars` style is only relevant to 2-d data plotting.  It is a
        !          5041:  combination of the `boxes` and `yerrorbars` styles.  The boxwidth will come
        !          5042:  from the fourth column if the y errors are in the form of "ydelta" and the
        !          5043:  boxwidth was not previously set equal to -2.0 (`set boxwidth -2.0`) or from
        !          5044:  the fifth column if the y errors are in the form of "ylow yhigh".  The
        !          5045:  special case  `boxwidth = -2.0` is for four-column data with y errors in the
        !          5046:  form "ylow yhigh".  In this case the boxwidth will be calculated so that each
        !          5047:  box touches the adjacent boxes.  The width will also be calculated in cases
        !          5048:  where three-column data are used.
        !          5049:
        !          5050:  The box height is determined from the y error in the same way as it is for
        !          5051:  the `yerrorbars` style---either from y-ydelta to y+ydelta or from ylow to
        !          5052:  yhigh, depending on how many data columns are provided.
        !          5053: ^<a href="http://www.nas.nasa.gov/~woo/gnuplot/errorbar/errorbar.html"> See Demo. </a>
        !          5054: 4 boxes
        !          5055: ?commands set style boxes
        !          5056: ?commands set style bargraph
        !          5057: ?set style boxes
        !          5058: ?set style bargraph
        !          5059: ?style boxes
        !          5060: ?style bargraph
        !          5061: ?boxes
        !          5062: ?bargraph
        !          5063:  The `boxes` style is only relevant to 2-d plotting.  It draws a box centered
        !          5064:  about the given x coordinate from the x axis (not the graph border) to the
        !          5065:  given y coordinate.  The width of the box is obtained in one of three ways.
        !          5066:  If it is a data plot and the data file has a third column, this will be used
        !          5067:  to set the width of the box.  If not, if a width has been set using the `set
        !          5068:  boxwidth` command, this will be used.  If neither of these is available, the
        !          5069:  width of each box will be calculated automatically so that it touches the
        !          5070:  adjacent boxes.
        !          5071: 4 boxxyerrorbars
        !          5072: ?commands set style boxxyerrorbars
        !          5073: ?set style boxxyerrorbars
        !          5074: ?style boxxyerrorbars
        !          5075: ?boxxyerrorbars
        !          5076:  The `boxxyerrorbars` style is only relevant to 2-d data plotting.  It is a
        !          5077:  combination of the `boxes` and `xyerrorbars` styles.
        !          5078:
        !          5079:  The box width and height are determined from the x and y errors in the same
        !          5080:  way as they are for the `xyerrorbars` style---either from xlow to xhigh and
        !          5081:  from ylow to yhigh, or from x-xdelta to x+xdelta and from y-ydelta to
        !          5082:  y+ydelta , depending on how many data columns are provided.
        !          5083: 4 candlesticks
        !          5084: ?commands set style candlesticks
        !          5085: ?set style candlesticks
        !          5086: ?style candlesticks
        !          5087: ?candlesticks
        !          5088:  The `candlesticks` style is only relevant for 2-d data plotting of financial
        !          5089:  data.  Five columns of data are required; in order, these should be the x
        !          5090:  coordinate (most likely a date) and the opening, low, high, and closing
        !          5091:  prices.  The symbol is an open rectangle, centered horizontally at the x
        !          5092:  coordinate and limited vertically by the opening and closing prices.  A
        !          5093:  vertical line segment at the x coordinate extends up from the top of the
        !          5094:  rectangle to the high price and another down to the low.  The width of the
        !          5095:  rectangle may be changed by `set bar`.  The symbol will be unchanged if the
        !          5096:  low and high prices are interchanged or if the opening and closing prices
        !          5097:  are interchanged.  See `set bar` and `financebars`.
        !          5098: ^<a href="http://www.nas.nasa.gov/~woo/gnuplot/finance/finance.html"> See demos.</a>
        !          5099: 4 dots
        !          5100: ?commands set style dots
        !          5101: ?set style dots
        !          5102: ?style dots
        !          5103: ?dots
        !          5104:  The `dots` style plots a tiny dot at each point; this is useful for scatter
        !          5105:  plots with many points.
        !          5106: 4 financebars
        !          5107: ?commands set style financebars
        !          5108: ?set style financebars
        !          5109: ?style financebars
        !          5110: ?financebars
        !          5111:  The `financebars` style is only relevant for 2-d data plotting of financial
        !          5112:  data.  Five columns of data are required; in order, these should be the x
        !          5113:  coordinate (most likely a date) and the opening, low, high, and closing
        !          5114:  prices.  The symbol is a vertical line segment, located horizontally at the x
        !          5115:  coordinate and limited vertically by the high and low prices.  A horizontal
        !          5116:  tic on the left marks the opening price and one on the right marks the
        !          5117:  closing price.  The length of these tics may be changed by `set bar`.  The
        !          5118:  symbol will be unchanged if the high and low prices are interchanged.  See
        !          5119:  `set bar` and `candlesticks`.
        !          5120: ^<a href="http://www.nas.nasa.gov/~woo/gnuplot/finance/finance.html"> See demos.</a>
        !          5121: 4 fsteps
        !          5122: ?commands set style fsteps
        !          5123: ?set style fsteps
        !          5124: ?style fsteps
        !          5125: ?fsteps
        !          5126:  The `fsteps` style is only relevant to 2-d plotting.  It connects consecutive
        !          5127:  points with two line segments: the first from (x1,y1) to (x1,y2) and the
        !          5128:  second from (x1,y2) to (x2,y2).
        !          5129: ^<a href="http://www.nas.nasa.gov/~woo/gnuplot/steps/steps.html"> See demo. </a>
        !          5130: 4 histeps
        !          5131: ?commands set style histeps
        !          5132: ?set style histeps
        !          5133: ?style histeps
        !          5134: ?histeps
        !          5135:  The `histeps` style is only relevant to 2-d plotting.  It is intended for
        !          5136:  plotting histograms.  Y-values are assumed to be centered at the x-values;
        !          5137:  the point at x1 is represented as a horizontal line from ((x0+x1)/2,y1) to
        !          5138:  ((x1+x2)/2,y1).  The lines representing the end points are extended so that
        !          5139:  the step is centered on at x.  Adjacent points are connected by a vertical
        !          5140:  line at their average x, that is, from ((x1+x2)/2,y1) to ((x1+x2)/2,y2).
        !          5141:
        !          5142:  If `autoscale` is in effect, it selects the xrange from the data rather than
        !          5143:  the steps, so the end points will appear only half as wide as the others.
        !          5144: ^<a href="http://www.nas.nasa.gov/~woo/gnuplot/steps/steps.html"> See demo. </a>
        !          5145:
        !          5146:  `histeps` is only a plotting style; `gnuplot` does not have the ability to
        !          5147:  create bins and determine their population from some data set.
        !          5148: 4 impulses
        !          5149: ?commands set style impulses
        !          5150: ?set style impulses
        !          5151: ?style impulses
        !          5152: ?impulses
        !          5153:  The `impulses` style displays a vertical line from the x axis (not the graph
        !          5154:  border), or from the grid base for `splot`, to each point.
        !          5155: 4 lines
        !          5156: ?commands set style lines
        !          5157: ?set style lines
        !          5158: ?style lines
        !          5159: ?lines
        !          5160:  The `lines` style connects adjacent points with straight line segments.
        !          5161: 4 linespoints
        !          5162: ?commands set style linespoints
        !          5163: ?commands set style lp
        !          5164: ?set style linespoints
        !          5165: ?set style lp
        !          5166: ?style linespoints
        !          5167: ?style lp
        !          5168: ?linespoints
        !          5169: ?lp
        !          5170:  The `linespoints` style does both `lines` and `points`, that is, it draws a
        !          5171:  small symbol at each point and then connects adjacent points with straight
        !          5172:  line segments.  The command `set pointsize` may be used to change the size of
        !          5173:  the points.  See `set pointsize` for its usage.
        !          5174:
        !          5175:  `linespoints` may be abbreviated `lp`.
        !          5176: 4 points
        !          5177: ?commands set style points
        !          5178: ?set style points
        !          5179: ?style points
        !          5180: ?points
        !          5181:  The `points` style displays a small symbol at each point.  The command `set
        !          5182:  pointsize` may be used to change the size of the points.  See `set pointsize`
        !          5183:  for its usage.
        !          5184: 4 steps
        !          5185: ?commands set style steps
        !          5186: ?set style steps
        !          5187: ?style steps
        !          5188: ?steps
        !          5189:  The `steps` style is only relevant to 2-d plotting.  It connects consecutive
        !          5190:  points with two line segments: the first from (x1,y1) to (x2,y1) and the
        !          5191:  second from (x2,y1) to (x2,y2).
        !          5192: ^<a href="http://www.nas.nasa.gov/~woo/gnuplot/steps/steps.html"> See demo. </a>
        !          5193: 4 vector
        !          5194: ?commands set style vector
        !          5195: ?set style vector
        !          5196: ?style vector
        !          5197: ?vector
        !          5198:  The `vector` style draws a vector from (x,y) to (x+xdelta,y+ydelta).  Thus
        !          5199:  it requires four columns of data.  It also draws a small arrowhead at the
        !          5200:  end of the vector.
        !          5201:
        !          5202:  The `vector` style is still experimental: it doesn't get clipped properly
        !          5203:  and other things may also be wrong with it.  Use it at your own risk.
        !          5204: 4 xerrorbars
        !          5205: ?commands set style xerrorbars
        !          5206: ?set style xerrorbars
        !          5207: ?style xerrorbars
        !          5208: ?xerrorbars
        !          5209:  The `xerrorbars` style is only relevant to 2-d data plots.  `xerrorbars` is
        !          5210:  like `dots`, except that a horizontal error bar is also drawn.  At each point
        !          5211:  (x,y), a line is drawn from (xlow,y) to (xhigh,y) or from (x-xdelta,y) to
        !          5212:  (x+xdelta,y), depending on how many data columns are provided.  A tic mark
        !          5213:  is placed at the ends of the error bar (unless `set bar` is used---see `set
        !          5214:  bar` for details).
        !          5215: 4 xyerrorbars
        !          5216: ?commands set style xyerrorbars
        !          5217: ?set style xyerrorbars
        !          5218: ?style xyerrorbars
        !          5219: ?xyerrorbars
        !          5220:  The `xyerrorbars` style is only relevant to 2-d data plots.  `xyerrorbars` is
        !          5221:  like `dots`, except that horizontal and vertical error bars are also drawn.
        !          5222:  At each point (x,y), lines are drawn from (x,y-ydelta) to (x,y+ydelta) and
        !          5223:  from (x-xdelta,y) to (x+xdelta,y) or from (x,ylow) to (x,yhigh) and from
        !          5224:  (xlow,y) to (xhigh,y), depending upon the number of data columns provided.  A
        !          5225:  tic mark is placed at the ends of the error bar (unless `set bar` is
        !          5226:  used---see `set bar` for details).
        !          5227:
        !          5228:  If data are provided in an unsupported mixed form, the `using` filter on the
        !          5229:  `plot` command should be used to set up the appropriate form.  For example,
        !          5230:  if the data are of the form (x,y,xdelta,ylow,yhigh), then you can use
        !          5231:
        !          5232:        plot 'data' using 1:2:($1-$3),($1+$3),4,5 with xyerrorbars
        !          5233: 4 yerrorbars
        !          5234: ?commands set style yerrorbars
        !          5235: ?commands set style errorbars
        !          5236: ?set style yerrorbars
        !          5237: ?set style errorbars
        !          5238: ?style yerrorbars
        !          5239: ?style errorbars
        !          5240: ?yerrorbars
        !          5241: ?errorbars
        !          5242:  The `yerrorbars` (or `errorbars`) style is only relevant to 2-d data plots.
        !          5243:  `yerrorbars` is like `dots`, except that a vertical error bar is also drawn.
        !          5244:  At each point (x,y), a line is drawn from (x,y-ydelta) to (x,y+ydelta) or
        !          5245:  from (x,ylow) to (x,yhigh), depending on how many data columns are provided.
        !          5246:  A tic mark is placed at the ends of the error bar (unless `set bar` is
        !          5247:  used---see `set bar` for details).
        !          5248: ^<a href="http://www.nas.nasa.gov/~woo/gnuplot/errorbar/errorbar.html"> See demo. </a>
        !          5249: 3 surface
        !          5250: ?commands set surface
        !          5251: ?commands set nosurface
        !          5252: ?commands show surface
        !          5253: ?set surface
        !          5254: ?set nosurface
        !          5255: ?show surface
        !          5256: ?surface
        !          5257: ?nosurface
        !          5258:  The command `set surface` controls the display of surfaces by `splot`.
        !          5259:
        !          5260:  Syntax:
        !          5261:        set surface
        !          5262:        set nosurface
        !          5263:        show surface
        !          5264:
        !          5265:  The surface is drawn with the style specifed by `with`, or else the
        !          5266:  appropriate style, data or function.
        !          5267:
        !          5268:  Whenever `set nosurface` is issued, `splot` will not draw points or lines
        !          5269:  corresponding to the function or data file points.  Contours may be still be
        !          5270:  drawn on the surface, depending on the `set contour` option. `set nosurface;
        !          5271:  set contour base` is useful for displaying contours on the grid base.  See
        !          5272:  also `set contour`.
        !          5273: ^ <h2> Terminal Types </h2>
        !          5274: 3 terminal
        !          5275: ?commands set terminal
        !          5276: ?commands show terminal
        !          5277: ?set terminal
        !          5278: ?set term
        !          5279: ?show terminal
        !          5280: ?terminal
        !          5281: ?term
        !          5282:  `gnuplot` supports many different graphics devices.  Use `set terminal` to
        !          5283:  tell `gnuplot` what kind of output to generate. Use `set output` to redirect
        !          5284:  that output to a file or device.
        !          5285:
        !          5286:  Syntax:
        !          5287:        set terminal {<terminal-type>}
        !          5288:        show terminal
        !          5289:
        !          5290:  If <terminal-type> is omitted, `gnuplot` will list the available terminal
        !          5291:  types.  <terminal-type> may be abbreviated.
        !          5292:
        !          5293:  If both `set terminal` and `set output` are used together, it is safest to
        !          5294:  give `set terminal` first, because some terminals set a flag which is needed
        !          5295:  in some operating systems.
        !          5296:
        !          5297:  Several terminals have additional options.  For example, see `dumb`,
        !          5298:  `iris4d`, `hpljii` or `postscript`.
        !          5299:
        !          5300:  This document may describe drivers that are not available to you because they
        !          5301:  were not installed, or it may not describe all the drivers that are available
        !          5302:  to you, depending on its output format.
        !          5303: <4 -- all terminal stuff is pulled from the .trm files
        !          5304: 3 tics
        !          5305: ?commands set tics
        !          5306: ?commands show tics
        !          5307: ?set tics
        !          5308: ?show tics
        !          5309: ?tics
        !          5310:  The `set tics` command can be used to change the tics to be drawn outwards.
        !          5311:
        !          5312:  Syntax:
        !          5313:        set tics {<direction>}
        !          5314:        show tics
        !          5315:
        !          5316:  where <direction> may be `in` (the default) or `out`.
        !          5317:
        !          5318:  See also `set xtics` for more control of major (labelled) tic marks and `set
        !          5319:  mxtics` for control of minor tic marks.
        !          5320: 3 ticslevel
        !          5321: ?commands set ticslevel
        !          5322: ?commands show ticslevel
        !          5323: ?set ticslevel
        !          5324: ?show ticslevel
        !          5325: ?ticslevel
        !          5326:  Using `splot`, one can adjust the relative height of the vertical (Z) axis
        !          5327:  using `set ticslevel`.  The numeric argument provided specifies the location
        !          5328:  of the bottom of the scale (as a fraction of the z-range) above the xy-plane.
        !          5329:  The default value is 0.5.  Negative values are permitted, but tic labels on
        !          5330:  the three axes may overlap.
        !          5331:
        !          5332:  To place the xy-plane at a position 'pos' on the z-axis, `ticslevel` should
        !          5333:  be set equal to  (pos - zmin) / (zmin - zmax).
        !          5334:
        !          5335:  Syntax:
        !          5336:        set ticslevel {<level>}
        !          5337:        show tics
        !          5338:
        !          5339:  See also `set view`.
        !          5340: 3 ticscale
        !          5341: ?commands set ticscale
        !          5342: ?commands show ticscale
        !          5343: ?set ticscale
        !          5344: ?show ticscale
        !          5345: ?ticscale
        !          5346:  The size of the tic marks can be adjusted with `set ticscale`.
        !          5347:
        !          5348:  Syntax:
        !          5349:        set ticscale {<major> {<minor>}}
        !          5350:        show tics
        !          5351:
        !          5352:  If <minor> is not specified, it is 0.5*<major>.  The default size is 1.0 for
        !          5353:  major tics and 0.5 for minor tics.  Note that it is possible to have the tic
        !          5354:  marks pointing outward by specifying a negative size.
        !          5355: 3 timestamp
        !          5356: ?commands set timestamp
        !          5357: ?commands set time
        !          5358: ?commands set notimestamp
        !          5359: ?commands show timestamp
        !          5360: ?set timestamp
        !          5361: ?set time
        !          5362: ?set notimestamp
        !          5363: ?show timestamp
        !          5364: ?timestamp
        !          5365: ?notimestamp
        !          5366:  The command `set timestamp` places the time and date of the plot in the left
        !          5367:  margin.
        !          5368:
        !          5369:  Syntax:
        !          5370:        set timestamp {"<format>"} {top|bottom} {{no}rotate}
        !          5371:                      {<xoff>}{,<yoff>} {"<font>"}
        !          5372:        set notimestamp
        !          5373:        show timestamp
        !          5374:
        !          5375:  The format string allows you to choose the format used to write the date and
        !          5376:  time.  Its default value is what asctime() uses: "%a %b %d %H:%M:%S %Y"
        !          5377:  (weekday, month name, day of the month, hours, minutes, seconds, four-digit
        !          5378:  year).  With `top` or `bottom` you can place the timestamp at the top or
        !          5379:  bottom of the left margin (default: bottom).  `rotate` lets you write the
        !          5380:  timestamp vertically, if your terminal supports vertical text.  The constants
        !          5381:  <xoff> and <off> are offsets from the default position given in character
        !          5382:  screen coordinates.  <font> is used to specify the font with which the time
        !          5383:  is to be written.
        !          5384:
        !          5385:  The abbreviation `time` may be used in place of `timestamp`.
        !          5386:
        !          5387:  Example:
        !          5388:        set timestamp "%d/%m/%y %H:%M" 80,-2 "Helvetica"
        !          5389:
        !          5390:  See `set timefmt` for more information about time format strings.
        !          5391: 3 timefmt
        !          5392: ?commands set timefmt
        !          5393: ?commands show timefmt
        !          5394: ?set timefmt
        !          5395: ?show timefmt
        !          5396: ?timefmt
        !          5397:  This command applies to timeseries where data are composed of dates/times.
        !          5398:  It has no meaning unless the command `set xdata time` is given also.
        !          5399:
        !          5400:  Syntax:
        !          5401:        set timefmt "<format string>"
        !          5402:        show timefmt
        !          5403:
        !          5404:  The string argument tells `gnuplot` how to read timedata from the datafile.
        !          5405:  The valid formats are:
        !          5406:
        !          5407: @start table - first is interactive cleartext form
        !          5408:        Format       Explanation
        !          5409:        %d           day of the month, 1--31
        !          5410:        %m           month of the year, 1--12
        !          5411:        %y           year, 0--99
        !          5412:        %Y           year, 4-digit
        !          5413:        %j           day of the year, 1--365
        !          5414:        %H           hour, 0--24
        !          5415:        %M           minute, 0--60
        !          5416:        %S           second, 0--60
        !          5417:        %b           three-character abbreviation of the name of the month
        !          5418:        %B           name of the month
        !          5419: #\begin{tabular}{|cl|} \hline
        !          5420: #\multicolumn{2}{|c|}{Time Series timedata Format Specifiers}\\
        !          5421: #\hline \hline
        !          5422: #Format & Explanation \\ \hline
        !          5423: #\verb@%d@ & day of the month, 1--31 \\
        !          5424: #\verb@%m@ & month of the year, 1--12 \\
        !          5425: #\verb@%y@ & year, 0--99 \\
        !          5426: #\verb@%Y@ & year, 4-digit \\
        !          5427: #\verb@%j@ & day of the year, 1--365 \\
        !          5428: #\verb@%H@ & hour, 0--24 \\
        !          5429: #\verb@%M@ & minute, 0--60 \\
        !          5430: #\verb@%S@ & second, 0--60 \\
        !          5431: #\verb@%b@ & three-character abbreviation of the name of the month \\
        !          5432: #\verb@%B@ & name of the month \\
        !          5433: %c l .
        !          5434: %Format@Explanation
        !          5435: %_
        !          5436: %%d@day of the month, 1--31
        !          5437: %%m@month of the year, 1--12
        !          5438: %%y@year, 0--99
        !          5439: %%Y@year, 4-digit
        !          5440: %%j@day of the year, 1--365
        !          5441: %%H@hour, 0--24
        !          5442: %%M@minute, 0--60
        !          5443: %%S@second, 0--60
        !          5444: %%b@three-character abbreviation of the name of the month
        !          5445: %%B@name of the month
        !          5446: %_
        !          5447: @end table
        !          5448:  Any character is allowed in the string, but must match exactly.  \t (tab) is
        !          5449:  recognized.  Backslash-octals (\nnn) are converted to char.  If there is no
        !          5450:  separating character between the time/date elements, then %d, %m, %y, %H, %M
        !          5451:  and %S read two digits each, %Y reads four digits and %j reads three digits.
        !          5452:  %b requires three characters, and %B requires as many as it needs.
        !          5453:
        !          5454:  Spaces are treated slightly differently.  A space in the string stands for
        !          5455:  zero or more whitespace characters in the file.  That is, "%H %M" can be used
        !          5456:  to read "1220" and "12     20" as well as "12 20".
        !          5457:
        !          5458:  Each set of non-blank characters in the timedata counts as one column in the
        !          5459:  `using n:n` specification.  Thus `11:11  25/12/76  21.0` consists of three
        !          5460:  columns.  To avoid confusion, `gnuplot` requires that you provide a complete
        !          5461:  `using` specification if your file contains timedata.
        !          5462:
        !          5463:  Since `gnuplot` cannot read non-numerical text, if the date format includes
        !          5464:  the day or month in words, the format string must exclude this text.  But
        !          5465:  it can still be printed with the "%a", "%A", "%b", or "%B" specifier: see
        !          5466:  `set format` for more details about these and other options for printing
        !          5467:  timedata.  (`gnuplot` will determine the proper month and weekday from the
        !          5468:  numerical values.)
        !          5469:
        !          5470:  See also `set xdata` and `Time/date` for more information.
        !          5471:
        !          5472:  Example:
        !          5473:        set timefmt "%d/%m/%Y\t%H:%M"
        !          5474:  tells `gnuplot` to read date and time separated by tab.  (But look closely at
        !          5475:  your data---what began as a tab may have been converted to spaces somewhere
        !          5476:  along the line; the format string must match what is actually in the file.)
        !          5477: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/timedat/timedat.html"> Time Data Demo </a>
        !          5478: 3 title
        !          5479: ?commands set title
        !          5480: ?commands show title
        !          5481: ?set title
        !          5482: ?show title
        !          5483: ?title
        !          5484:  The `set title` command produces a plot title that is centered at the top of
        !          5485:  the plot.  `set title` is a special case of `set label`.
        !          5486:
        !          5487:  Syntax:
        !          5488:        set title {"<title-text>"} {<xoff>}{,<yoff>} {"<font>,{<size>}"}
        !          5489:        show title
        !          5490:
        !          5491:  Specifying constants <xoff> or <yoff> as optional offsets for the title will
        !          5492:  move the title <xoff> or <yoff> character screen coordinates (not graph
        !          5493:  coordinates).  For example, "`set title ,-1`" will change only the y offset
        !          5494:  of the title, moving the title down by roughly the height of one character.
        !          5495:
        !          5496:  <font> is used to specify the font with which the title is to be written;
        !          5497:  the units of the font <size> depend upon which terminal is used.
        !          5498:
        !          5499:  `set title` with no parameters clears the title.
        !          5500:
        !          5501:  See `syntax` for details about the processing of backslash sequences and
        !          5502:  the distinction between single- and double-quotes.
        !          5503: 3 tmargin
        !          5504: ?commands set tmargin
        !          5505: ?set tmargin
        !          5506: ?tmargin
        !          5507:  The command `set tmargin` sets the size of the top margin.  Please see
        !          5508:  `set margin` for details.
        !          5509: 3 trange
        !          5510: ?commands set trange
        !          5511: ?commands show trange
        !          5512: ?set trange
        !          5513: ?show trange
        !          5514: ?trange
        !          5515:  The `set trange` command sets the parametric range used to compute x and y
        !          5516:  values when in parametric or polar modes.  Please see `set xrange` for
        !          5517:  details.
        !          5518: 3 urange
        !          5519: ?commands set urange
        !          5520: ?commands show urange
        !          5521: ?set urange
        !          5522: ?show urange
        !          5523: ?urange
        !          5524:  The `set urange` and `set vrange` commands set the parametric ranges used
        !          5525:  to compute x, y, and z values when in `splot` parametric mode.  Please see
        !          5526:  `set xrange` for details.
        !          5527: 3 variables
        !          5528: ?commands show variables
        !          5529: ?show variables
        !          5530:  The `show variables` command lists all user-defined variables and their
        !          5531:  values.
        !          5532:
        !          5533:  Syntax:
        !          5534:        show variables
        !          5535: 3 version
        !          5536: ?show version
        !          5537:  The `show version` command lists the version of gnuplot being run, its last
        !          5538:  modification date, the copyright holders, and email addresses for the FAQ,
        !          5539:  the info-gnuplot mailing list, and reporting bugs--in short, the information
        !          5540:  listed on the screen when the program is invoked interactively.
        !          5541:
        !          5542:  Syntax:
        !          5543:        show version {long}
        !          5544:
        !          5545:  When the `long` option is given, it also lists the operating system, the
        !          5546:  compilation options used when `gnuplot` was installed, the location of the
        !          5547:  help file, and (again) the useful email addresses.
        !          5548: 3 view
        !          5549: ?commands set view
        !          5550: ?commands show view
        !          5551: ?set view
        !          5552: ?show view
        !          5553: ?view
        !          5554:  The `set view` command sets the viewing angle for `splot`s.  It controls how
        !          5555:  the 3-d coordinates of the plot are mapped into the 2-d screen space.  It
        !          5556:  provides controls for both rotation and scaling of the plotted data, but
        !          5557:  supports orthographic projections only.
        !          5558:
        !          5559:  Syntax:
        !          5560:        set view <rot_x> {,{<rot_z>}{,{<scale>}{,<scale_z>}}}
        !          5561:        show view
        !          5562:
        !          5563:  where <rot_x> and <rot_z> control the rotation angles (in degrees) in a
        !          5564:  virtual 3-d coordinate system aligned with the screen such that initially
        !          5565:  (that is, before the rotations are performed) the screen horizontal axis is
        !          5566:  x, screen vertical axis is y, and the axis perpendicular to the screen is z.
        !          5567:  The first rotation applied is <rot_x> around the x axis.  The second rotation
        !          5568:  applied is <rot_z> around the new z axis.
        !          5569:
        !          5570:  <rot_x> is bounded to the [0:180] range with a default of 60 degrees, while
        !          5571:  <rot_z> is bounded to the [0:360] range with a default of 30 degrees.
        !          5572:  <scale> controls the scaling of the entire `splot`, while <scale_z> scales
        !          5573:  the z axis only.  Both scales default to 1.0.
        !          5574:
        !          5575:  Examples:
        !          5576:        set view 60, 30, 1, 1
        !          5577:        set view ,,0.5
        !          5578:
        !          5579:  The first sets all the four default values.  The second changes only scale,
        !          5580:  to 0.5.
        !          5581:
        !          5582:  See also `set ticslevel`.
        !          5583: 3 vrange
        !          5584: ?commands set vrange
        !          5585: ?commands show vrange
        !          5586: ?set vrange
        !          5587: ?show vrange
        !          5588: ?vrange
        !          5589:  The `set urange` and `set vrange` commands set the parametric ranges used
        !          5590:  to compute x, y, and z values when in `splot` parametric mode.  Please see
        !          5591:  `set xrange` for details.
        !          5592: 3 x2data
        !          5593: ?commands set x2data
        !          5594: ?commands show x2data
        !          5595: ?set x2data
        !          5596: ?show x2data
        !          5597: ?x2data
        !          5598:  The `set x2data` command sets data on the x2 (top) axis to timeseries
        !          5599:  (dates/times).  Please see `set xdata`.
        !          5600: 3 x2dtics
        !          5601: ?commands set x2dtics
        !          5602: ?commands set nox2dtics
        !          5603: ?commands show x2dtics
        !          5604: ?set x2dtics
        !          5605: ?set nox2dtics
        !          5606: ?show x2dtics
        !          5607: ?x2dtics
        !          5608: ?nox2dtics
        !          5609:  The `set x2dtics` command changes tics on the x2 (top) axis to days of the
        !          5610:  week.  Please see `set xdtics` for details.
        !          5611: 3 x2label
        !          5612: ?commands set x2label
        !          5613: ?commands show x2label
        !          5614: ?set x2label
        !          5615: ?show x2label
        !          5616: ?x2label
        !          5617:  The `set x2label` command sets the label for the x2 (top) axis.  Please see
        !          5618:  `set xlabel`.
        !          5619: 3 x2mtics
        !          5620: ?commands set x2mtics
        !          5621: ?commands set nox2mtics
        !          5622: ?commands show x2mtics
        !          5623: ?set x2mtics
        !          5624: ?set nox2mtics
        !          5625: ?show x2mtics
        !          5626: ?x2mtics
        !          5627: ?nox2mtics
        !          5628:  The `set x2mtics` command changes tics on the x2 (top) axis to months of the
        !          5629:  year.  Please see `set xmtics` for details.
        !          5630: 3 x2range
        !          5631: ?commands set x2range
        !          5632: ?commands show x2range
        !          5633: ?set x2range
        !          5634: ?show x2range
        !          5635: ?x2range
        !          5636:  The `set x2range` command sets the horizontal range that will be displayed on
        !          5637:  the x2 (top) axis.  Please see `set xrange` for details.
        !          5638: 3 x2tics
        !          5639: ?commands set x2tics
        !          5640: ?commands set nox2tics
        !          5641: ?commands show x2tics
        !          5642: ?set x2tics
        !          5643: ?set nox2tics
        !          5644: ?show x2tics
        !          5645: ?x2tics
        !          5646: ?nox2tics
        !          5647:  The `set x2tics` command controls major (labelled) tics on the x2 (top) axis.
        !          5648:  Please see `set xtics` for details.
        !          5649: 3 x2zeroaxis
        !          5650: ?commands set x2zeroaxis
        !          5651: ?commands set nox2zeroaxis
        !          5652: ?commands show x2zeroaxis
        !          5653: ?set x2zeroaxis
        !          5654: ?set nox2zeroaxis
        !          5655: ?show x2zeroaxis
        !          5656: ?x2zeroaxis
        !          5657: ?nox2zeroaxis
        !          5658:  The `set x2zeroaxis` command draws a line at the origin of the x2 (top) axis
        !          5659:  (y2 = 0).  For details, please see
        !          5660:  `set zeroaxis`.
        !          5661: 3 xdata
        !          5662: ?commands set xdata
        !          5663: ?commands show xdata
        !          5664: ?set xdata
        !          5665: ?show xdata
        !          5666: ?xdata
        !          5667:  This command sets the datatype on the x axis to time/date.  A similar command
        !          5668:  does the same thing for each of the other axes.
        !          5669:
        !          5670:  Syntax:
        !          5671:        set xdata {time}
        !          5672:        show xdata
        !          5673:
        !          5674:  The same syntax applies to `ydata`, `zdata`, `x2data` and `y2data`.
        !          5675:
        !          5676:  The `time` option signals that the datatype is indeed time/date.  If the
        !          5677:  option is not specified, the datatype reverts to normal.
        !          5678:
        !          5679:  See `set timefmt` to tell `gnuplot` how to read date or time data.  The
        !          5680:  time/date is converted to seconds from start of the century.  There is
        !          5681:  currently only one timefmt, which implies that all the time/date columns must
        !          5682:  confirm to this format.  Specification of ranges should be supplied as quoted
        !          5683:  strings according to this format to avoid interpretation of the time/date as
        !          5684:  an expression.
        !          5685:
        !          5686:  The function 'strftime' (type "man strftime" on unix to look it up) is used
        !          5687:  to print tic-mark labels.  `gnuplot` tries to figure out a reasonable format
        !          5688:  for this  unless the `set format x "string"` has supplied something that does
        !          5689:  not look like a decimal format (more than one '%' or neither %f nor %g).
        !          5690:
        !          5691:  See also `Time/date` for more information.
        !          5692: 3 xdtics
        !          5693: ?commands set xdtics
        !          5694: ?commands set noxdtics
        !          5695: ?commands show xdtics
        !          5696: ?set xdtics
        !          5697: ?set noxdtics
        !          5698: ?show xdtics
        !          5699: ?xdtics
        !          5700: ?noxdtics
        !          5701:  The `set xdtics` commands converts the x-axis tic marks to days of the week
        !          5702:  where 0=Sun and 6=Sat.  Overflows are converted modulo 7 to dates.  `set
        !          5703:  noxdtics` returns the labels to their default values.  Similar commands do
        !          5704:  the same things for the other axes.
        !          5705:
        !          5706:  Syntax:
        !          5707:        set xdtics
        !          5708:        set noxdtics
        !          5709:        show xdtics
        !          5710:
        !          5711:  The same syntax applies to `ydtics`, `zdtics`, `x2dtics` and `y2dtics`.
        !          5712:
        !          5713:  See also the `set format` command.
        !          5714: 3 xlabel
        !          5715: ?commands set xlabel
        !          5716: ?commands show xlabel
        !          5717: ?set xlabel
        !          5718: ?show xlabel
        !          5719: ?xlabel
        !          5720:  The `set xlabel` command sets the x axis label.  Similar commands set labels
        !          5721:  on the other axes.
        !          5722:
        !          5723:  Syntax:
        !          5724:        set xlabel {"<label>"} {<xoff>}{,<yoff>} {"<font>{,<size>}"}
        !          5725:        show xlabel
        !          5726:
        !          5727:  The same syntax applies to `x2label`, `ylabel`, `y2label` and `zlabel`.
        !          5728:
        !          5729:  Specifying the constants <xoff> or <yoff> as optional offsets for a label
        !          5730:  will move it <xoff> or <yoff> character widths or heights.  For example,
        !          5731:  "` set xlabel -1`" will change only the x offset of the xlabel, moving the
        !          5732:  label roughly one character width to the left.   The size of a character
        !          5733:  depends on both the font and the terminal.
        !          5734:
        !          5735:  <font> is used to specify the font in which the label is written; the units
        !          5736:  of the font <size> depend upon which terminal is used.
        !          5737:
        !          5738:  To clear a label, put no options on the command line, e.g., "`set y2label`".
        !          5739:
        !          5740:  The default positions of the axis labels are as follows:
        !          5741:
        !          5742:  xlabel:  The x-axis label is centered below the bottom axis.
        !          5743:
        !          5744:  ylabel:  The position of the y-axis label depends on the terminal, and can be
        !          5745:  one of the following three positions:
        !          5746:
        !          5747:  1. Horizontal text flushed left at the top left of the plot.  Terminals that
        !          5748:  cannot rotate text will probably use this method.  If `set x2tics` is also
        !          5749:  in use, the ylabel may overwrite the left-most x2tic label.  This may be
        !          5750:  remedied by adjusting the ylabel position or the left margin.
        !          5751:
        !          5752:  2. Vertical text centered vertically at the left of the plot.  Terminals
        !          5753:  that can rotate text will probably use this method.
        !          5754:
        !          5755:  3. Horizontal text centered vertically at the left of the plot.  The EEPIC,
        !          5756:  LaTeX and TPIC drivers use this method.  The user must insert line breaks
        !          5757:  using \\ to prevent the ylabel from overwriting the plot.  To produce a
        !          5758:  vertical row of characters, add \\ between every printing character (but this
        !          5759:  is ugly).
        !          5760:
        !          5761:  zlabel: The z-axis label is centered along the z axis and placed in the space
        !          5762:  above the grid level.
        !          5763:
        !          5764:  y2label: The y2-axis label is placed to the right of the y2 axis.  The
        !          5765:  position is terminal-dependent in the same manner as is the y-axis label.
        !          5766:
        !          5767:  x2label: The x2-axis label is placed above the top axis but below the plot
        !          5768:  title.  It is also possible to create an x2-axis label by using new-line
        !          5769:  characters to make a multi-line plot title, e.g.,
        !          5770:
        !          5771:        set title "This is the title\n\nThis is the x2label"
        !          5772:
        !          5773:  Note that double quotes must be used.  The same font will be used for both
        !          5774:  lines, of course.
        !          5775:
        !          5776:  If you are not satisfied with the default position of an axis label, use `set
        !          5777:  label` instead--that command gives you much more control over where text is
        !          5778:  placed.
        !          5779:
        !          5780:  Please see `set syntax` for further information about backslash processing
        !          5781:  and the difference between single- and double-quoted strings.
        !          5782: 3 xmtics
        !          5783: ?commands set xmtics
        !          5784: ?commands set noxmtics
        !          5785: ?commands show xmtics
        !          5786: ?set xmtics
        !          5787: ?set noxmtics
        !          5788: ?show xmtics
        !          5789: ?xmtics
        !          5790: ?noxmtics
        !          5791:  The `set xmtics` commands converts the x-axis tic marks to months of the
        !          5792:  year where 1=Jan and 12=Dec.  Overflows are converted modulo 12 to months.
        !          5793:  The tics are returned to their default labels by `set noxmtics`.  Similar
        !          5794:  commands perform the same duties for the other axes.
        !          5795:
        !          5796:  Syntax:
        !          5797:        set xmtics
        !          5798:        set noxmtics
        !          5799:        show xmtics
        !          5800:
        !          5801:  The same syntax applies to `x2mtics`, `ymtics`, `y2mtics`, and `zmtics`.
        !          5802:
        !          5803:  See also the `set format` command.
        !          5804: 3 xrange
        !          5805: ?commands set xrange
        !          5806: ?commands show xrange
        !          5807: ?set xrange
        !          5808: ?show xrange
        !          5809: ?xrange
        !          5810:  The `set xrange` command sets the horizontal range that will be displayed.
        !          5811:  A similar command exists for each of the other axes, as well as for the
        !          5812:  polar radius r and the parametric variables t, u, and v.
        !          5813:
        !          5814:  Syntax:
        !          5815:        set xrange [{{<min>}:{<max>}}] {{no}reverse} {{no}writeback}
        !          5816:        show xrange
        !          5817:
        !          5818:  where <min> and <max> terms are constants, expressions or an asterisk to set
        !          5819:  autoscaling.  If the data are time/date, you must give the range as a quoted
        !          5820:  string according to the `set timefmt` format.  Any value omitted will not be
        !          5821:  changed.
        !          5822:
        !          5823:  The same syntax applies to `yrange`, `zrange`, `x2range`, `y2range`,
        !          5824:  `rrange`, `trange`, `urange` and `vrange`.
        !          5825:
        !          5826:  The `reverse` option reverses the direction of the axis, e.g., `set xrange
        !          5827:  [0:1] reverse` will produce an axis with 1 on the left and 0 on the right.
        !          5828:  This is identical to the axis produced by `set xrange [1:0]`, of course.
        !          5829:  `reverse` is intended primarily for use with `autoscale`.
        !          5830:
        !          5831:  The `writeback` option essentially saves the range found by `autoscale` in
        !          5832:  the buffers that would be filled by `set xrange`.  This is useful if you wish
        !          5833:  to plot several functions together but have the range determined by only
        !          5834:  some of them.  The `writeback` operation is performed during the `plot`
        !          5835:  execution, so it must be specified before that command.  For example,
        !          5836:
        !          5837:        set xrange [-10:10]
        !          5838:        set yrange [] writeback
        !          5839:        plot sin(x)
        !          5840:        set noautoscale y
        !          5841:        replot x/2
        !          5842:
        !          5843:  results in a yrange of [-1:1] as found only from the range of sin(x); the
        !          5844:  [-5:5] range of x/2 is ignored.  Executing `show yrange` after each command
        !          5845:  in the above example should help you understand what is going on.
        !          5846:
        !          5847:  In 2-d, `xrange` and `yrange` determine the extent of the axes, `trange`
        !          5848:  determines the range of the parametric variable in parametric mode or the
        !          5849:  range of the angle in polar mode.  Similarly in parametric 3-d, `xrange`,
        !          5850:  `yrange`, and `zrange` govern the axes and `urange` and `vrange` govern the
        !          5851:  parametric variables.
        !          5852:
        !          5853:  In polar mode, `rrange` determines the radial range plotted.  <rmin> acts as
        !          5854:  an additive constant to the radius, whereas <rmax> acts as a clip to the
        !          5855:  radius---no point with radius greater than <rmax> will be plotted.  `xrange`
        !          5856:  and `yrange` are affected---the ranges can be set as if the graph was of
        !          5857:  r(t)-rmin, with rmin added to all the labels.
        !          5858:
        !          5859:  Any range may be partially or totally autoscaled, although it may not make
        !          5860:  sense to autoscale a parametric variable unless it is plotted with data.
        !          5861:
        !          5862:  Ranges may also be specified on the `plot` command line.  A range given on
        !          5863:  the plot line will be used for that single `plot` command; a range given by
        !          5864:  a `set` command will be used for all subsequent plots that do not specify
        !          5865:  their own ranges.  The same holds true for `splot`.
        !          5866:
        !          5867:  Examples:
        !          5868:
        !          5869:  To set the xrange to the default:
        !          5870:        set xrange [-10:10]
        !          5871:
        !          5872:  To set the yrange to increase downwards:
        !          5873:        set yrange [10:-10]
        !          5874:
        !          5875:  To change zmax to 10 without affecting zmin (which may still be autoscaled):
        !          5876:        set zrange [:10]
        !          5877:
        !          5878:  To autoscale xmin while leaving xmax unchanged:
        !          5879:        set xrange [*:]
        !          5880: 3 xtics
        !          5881: ?commands set xtics
        !          5882: ?commands set noxtics
        !          5883: ?commands show xtics
        !          5884: ?set xtics
        !          5885: ?set noxtics
        !          5886: ?show xtics
        !          5887: ?xtics
        !          5888: ?noxtics
        !          5889:  Fine control of the major (labelled) tics on the x axis is possible with the
        !          5890:  `set xtics` command.  The tics may be turned off with the `set noxtics`
        !          5891:  command, and may be turned on (the default state) with `set xtics`.  Similar
        !          5892:  commands control the major tics on the y, z, x2 and y2 axes.
        !          5893:
        !          5894:  Syntax:
        !          5895:        set xtics {axis | border} {{no}mirror} {{no}rotate}
        !          5896:                  {  autofreq
        !          5897:                   | <incr>
        !          5898:                   | <start>, <incr> {,<end>}
        !          5899:                   | ({"<label>"} <pos> {,{"<label>"} <pos>}...) }
        !          5900:        set noxtics
        !          5901:        show xtics
        !          5902:
        !          5903:  The same syntax applies to `ytics`, `ztics`, `x2tics` and `y2tics`.
        !          5904:
        !          5905:  `axis` or `border` tells `gnuplot` to put the tics (both the tics themselves
        !          5906:  and the accompanying labels) along the axis or the border, respectively.
        !          5907:  `mirror` tells it to put unlabelled tics at the same positions on the
        !          5908:  opposite border.  `nomirror` does what you think it does.  `rotate` asks
        !          5909:  `gnuplot` to rotate the text through 90 degrees, if the underlying terminal
        !          5910:  driver supports text rotation.  `norotate` cancels this.  The defaults are
        !          5911:  `border mirror norotate` for tics on the x and y axes, and `border nomirror
        !          5912:  norotate` for tics on the x2 and y2 axes.  For the z axis, the the `{axis |
        !          5913:  border}` option is not available and the default is `nomirror`.  If you do
        !          5914:  want to mirror the z-axis tics, you might want to create a bit more room for
        !          5915:  them with `set border`.
        !          5916:
        !          5917:  `set xtics` with no options restores the default border if xtics are not
        !          5918:  being displayed;  otherwise it has no effect.  Any previously specified
        !          5919:  tic frequency or position {and labels} are retained.
        !          5920:
        !          5921:  Positions of the tics are calculated automatically by default or if the
        !          5922:  `autofreq` option is given; otherwise they may be specified in either of
        !          5923:  two forms:
        !          5924:
        !          5925:  The implicit <start>, <incr>, <end> form specifies that a series of tics will
        !          5926:  be plotted on the axis between the values <start> and <end> with an increment
        !          5927:  of <incr>.  If <end> is not given, it is assumed to be infinity.  The
        !          5928:  increment may be negative.  If neither <start> nor <end> is given, <start> is
        !          5929:  assumed to be negative infinity, <end> is assumed to be positive infinity,
        !          5930:  and the tics will be drawn at integral multiples of <step>.  If the axis is
        !          5931:  logarithmic, the increment will be used as a multiplicative factor.
        !          5932:
        !          5933:  Examples:
        !          5934:
        !          5935:  Make tics at 0, 0.5, 1, 1.5, ..., 9.5, 10.
        !          5936:        set xtics 0,.5,10
        !          5937:
        !          5938:  Make tics at ..., -10, -5, 0, 5, 10, ...
        !          5939:        set xtics 5
        !          5940:
        !          5941:  Make tics at 1, 100, 1e4, 1e6, 1e8.
        !          5942:        set logscale x; set xtics 1,100,10e8
        !          5943:
        !          5944:  The explicit ("<label>" <pos>, ...) form allows arbitrary tic positions or
        !          5945:  non-numeric tic labels.  A set of tics is a set of positions, each with its
        !          5946:  own optional label.  Note that the label is a string enclosed by quotes.  It
        !          5947:  may be a constant string, such as "hello", may contain formatting information
        !          5948:  for converting the position into its label, such as "%3f clients", or may be
        !          5949:  empty, "".  See `set format` for more information.  If no string is given,
        !          5950:  the default label (numerical) is used.  In this form, the tics do not need to
        !          5951:  be listed in numerical order.
        !          5952:
        !          5953:  Examples:
        !          5954:        set xtics ("low" 0, "medium" 50, "high" 100)
        !          5955:        set xtics (1,2,4,8,16,32,64,128,256,512,1024)
        !          5956:        set ytics ("bottom" 0, "" 10, "top" 20)
        !          5957:
        !          5958:  In the second example, all tics are labelled.  In the third, only the end
        !          5959:  tics are labelled.
        !          5960:
        !          5961:  However they are specified, tics will only be plotted when in range.
        !          5962:
        !          5963:  Format (or omission) of the tic labels is controlled by `set format`, unless
        !          5964:  the explicit text of a labels is included in the `set xtic (`<label>`)` form.
        !          5965:
        !          5966:  Minor (unlabelled) tics can be added by the `set mxtics` command.
        !          5967:
        !          5968:  In case of timeseries data, position values must be given as quoted dates
        !          5969:  or times according to the format `timefmt`.  If the <start>, <incr>, <end>
        !          5970:  form is used, <start> and <end> must be given according to `timefmt`, but
        !          5971:  <incr> must be in seconds.  Times will be written out according to the format
        !          5972:  given on `set format`, however.
        !          5973:
        !          5974:  Examples:
        !          5975:        set xdata time
        !          5976:        set timefmt "%d/%m"
        !          5977:        set format x "%b %d"
        !          5978:        set xrange ["01/12":"06/12"]
        !          5979:        set xtics "01/12", 172800, "05/12"
        !          5980:
        !          5981:        set xdata time
        !          5982:        set timefmt "%d/%m"
        !          5983:        set format x "%b %d"
        !          5984:        set xrange ["01/12":"06/12"]
        !          5985:        set xtics ("01/12", "" "03/12", "05/12")
        !          5986:  Both of these will produce tics "Dec 1", "Dec 3", and "Dec 5", but in the
        !          5987:  second example the tic at "Dec 3" will be unlabelled.
        !          5988:
        !          5989: 3 xzeroaxis
        !          5990: ?commands set xzeroaxis
        !          5991: ?commands set noxzeroaxis
        !          5992: ?commands show xzeroaxis
        !          5993: ?set xzeroaxis
        !          5994: ?set noxzeroaxis
        !          5995: ?show xzeroaxis
        !          5996: ?xzeroaxis
        !          5997: ?noxzeroaxis
        !          5998:  The `set xzeroaxis` command draws a line at y = 0.  For details, please see
        !          5999:  `set zeroaxis`.
        !          6000: 3 y2data
        !          6001: ?commands set y2data
        !          6002: ?commands show y2data
        !          6003: ?set y2data
        !          6004: ?show y2data
        !          6005: ?y2data
        !          6006:  The `set y2data` command sets y2 (right-hand) axis data to timeseries
        !          6007:  (dates/times).  Please see `set xdata`.
        !          6008: 3 y2dtics
        !          6009: ?commands set y2dtics
        !          6010: ?commands set noy2dtics
        !          6011: ?set y2dtics
        !          6012: ?set noy2dtics
        !          6013: ?show y2dtics
        !          6014: ?y2dtics
        !          6015: ?noy2dtics
        !          6016:  The `set y2dtics` command changes tics on the y2 (right-hand) axis to days of
        !          6017:  the week.  Please see `set xdtics` for details.
        !          6018: 3 y2label
        !          6019: ?commands set y2label
        !          6020: ?commands show y2label
        !          6021: ?set y2label
        !          6022: ?show y2label
        !          6023: ?y2label
        !          6024:  The `set y2dtics` command sets the label for the y2 (right-hand) axis.
        !          6025:  Please see `set xlabel`.
        !          6026: 3 y2mtics
        !          6027: ?commands set y2mtics
        !          6028: ?commands set noy2mtics
        !          6029: ?commands show y2mtics
        !          6030: ?set y2mtics
        !          6031: ?set noy2mtics
        !          6032: ?show y2mtics
        !          6033: ?y2mtics
        !          6034: ?noy2mtics
        !          6035:  The `set y2mtics` command changes tics on the y2 (right-hand) axis to months
        !          6036:  of the year.  Please see `set xmtics` for details.
        !          6037: 3 y2range
        !          6038: ?commands set y2range
        !          6039: ?commands show y2range
        !          6040: ?set y2range
        !          6041: ?show y2range
        !          6042: ?y2range
        !          6043:  The `set y2range` command sets the vertical range that will be displayed on
        !          6044:  the y2 (right-hand) axis.  Please see `set xrange` for details.
        !          6045: 3 y2tics
        !          6046: ?commands set y2tics
        !          6047: ?commands set noy2tics
        !          6048: ?commands show y2tics
        !          6049: ?set y2tics
        !          6050: ?set noy2tics
        !          6051: ?show y2tics
        !          6052: ?y2tics
        !          6053: ?noy2tics
        !          6054:  The `set y2tics` command controls major (labelled) tics on the y2 (right-hand)
        !          6055:  axis.  Please see `set xtics` for details.
        !          6056: 3 y2zeroaxis
        !          6057: ?commands set y2zeroaxis
        !          6058: ?commands set noy2zeroaxis
        !          6059: ?commands show y2zeroaxis
        !          6060: ?set y2zeroaxis
        !          6061: ?set noy2zeroaxis
        !          6062: ?show y2zeroaxis
        !          6063: ?y2zeroaxis
        !          6064: ?noy2zeroaxis
        !          6065:  The `set y2zeroaxis` command draws a line at the origin of the y2 (right-hand)
        !          6066:  axis (x2 = 0).  For details, please see `set zeroaxis`.
        !          6067: 3 ydata
        !          6068: ?commands set ydata
        !          6069: ?commands show ydata
        !          6070: ?set ydata
        !          6071: ?show ydata
        !          6072: ?ydata
        !          6073:  Sets y-axis data to timeseries (dates/times).  Please see `set xdata`.
        !          6074: 3 ydtics
        !          6075: ?commands set ydtics
        !          6076: ?commands set noydtics
        !          6077: ?commands show ydtics
        !          6078: ?set ydtics
        !          6079: ?set noydtics
        !          6080: ?show ydtics
        !          6081: ?ydtics
        !          6082: ?noydtics
        !          6083:  The `set ydtics` command changes tics on the y axis to days of the week.
        !          6084:  Please see `set xdtics` for details.
        !          6085: 3 ylabel
        !          6086: ?commands set ylabel
        !          6087: ?commands show ylabel
        !          6088: ?set ylabel
        !          6089: ?show ylabel
        !          6090: ?ylabel
        !          6091:  This command sets the label for the y axis.  Please see `set xlabel`.
        !          6092: 3 ymtics
        !          6093: ?commands set ymtics
        !          6094: ?commands set noymtics
        !          6095: ?commands show ymtics
        !          6096: ?set ymtics
        !          6097: ?set noymtics
        !          6098: ?show ymtics
        !          6099: ?ymtics
        !          6100: ?noymtics
        !          6101:  The `set ymtics` command changes tics on the y axis to months of the year.
        !          6102:  Please see `set xmtics` for details.
        !          6103: 3 yrange
        !          6104: ?commands set yrange
        !          6105: ?commands show yrange
        !          6106: ?set yrange
        !          6107: ?show yrange
        !          6108: ?yrange
        !          6109:  The `set yrange` command sets the vertical range that will be displayed on
        !          6110:  the y axis.  Please see `set xrange` for details.
        !          6111: 3 ytics
        !          6112: ?commands set ytics
        !          6113: ?commands set noytics
        !          6114: ?commands show ytics
        !          6115: ?set ytics
        !          6116: ?set noytics
        !          6117: ?show ytics
        !          6118: ?ytics
        !          6119: ?noytics
        !          6120:  The `set ytics` command controls major (labelled) tics on the y axis.
        !          6121:  Please see `set xtics` for details.
        !          6122: 3 yzeroaxis
        !          6123: ?commands set yzeroaxis
        !          6124: ?commands set noyzeroaxis
        !          6125: ?commands show yzeroaxis
        !          6126: ?set yzeroaxis
        !          6127: ?set noyzeroaxis
        !          6128: ?show yzeroaxis
        !          6129: ?yzeroaxis
        !          6130: ?noyzeroaxis
        !          6131:  The `set yzeroaxis` command draws a line at x = 0.  For details, please see
        !          6132:  `set zeroaxis`.
        !          6133: 3 zdata
        !          6134: ?commands set zdata
        !          6135: ?commands show zdata
        !          6136: ?set zdata
        !          6137: ?show zdata
        !          6138: ?zdata
        !          6139:  Set zaxis date to timeseries (dates/times).  Please see `set xdata`.
        !          6140: 3 zdtics
        !          6141: ?commands set zdtics
        !          6142: ?commands set nozdtics
        !          6143: ?commands show zdtics
        !          6144: ?set zdtics
        !          6145: ?set nozdtics
        !          6146: ?show zdtics
        !          6147: ?zdtics
        !          6148: ?nozdtics
        !          6149:  The `set zdtics` command changes tics on the z axis to days of the week.
        !          6150:  Please see `set xdtics` for details.
        !          6151: 3 zero
        !          6152: ?commands set zero
        !          6153: ?commands show zero
        !          6154: ?set zero
        !          6155: ?show zero
        !          6156: ?zero
        !          6157:  The `zero` value is the default threshold for values approaching 0.0.
        !          6158:
        !          6159:  Syntax:
        !          6160:        set zero <expression>
        !          6161:        show zero
        !          6162:
        !          6163:  `gnuplot` will not plot a point if its imaginary part is greater in magnitude
        !          6164:  than the `zero` threshold.  This threshold is also used in various other
        !          6165:  parts of `gnuplot` as a (crude) numerical-error threshold.  The default
        !          6166:  `zero` value is 1e-8.  `zero` values larger than 1e-3 (the reciprocal of the
        !          6167:  number of pixels in a typical bitmap display) should probably be avoided, but
        !          6168:  it is not unreasonable to set `zero` to 0.0.
        !          6169: 3 zeroaxis
        !          6170: ?commands set zeroaxis
        !          6171: ?commands set nozeroaxis
        !          6172: ?commands show zeroaxis
        !          6173: ?set zeroaxis
        !          6174: ?set nozeroaxis
        !          6175: ?show zeroaxis
        !          6176: ?zeroaxis
        !          6177: ?nozeroaxis
        !          6178:  The x axis may be drawn by `set xzeroaxis` and removed by `set noxzeroaxis`.
        !          6179:  Similar commands behave similarly for the y, x2, and y2 axes.
        !          6180:
        !          6181:  Syntax:
        !          6182:        set {x|x2|y|y2|}zeroaxis { {linestyle | ls <line_style>}
        !          6183:                                   | { linetype | lt <line_type>}
        !          6184:                                     { linewidth | lw <line_width>}}
        !          6185:        set no{x|x2|y|y2|}zeroaxis
        !          6186:        show {x|y|}zeroaxis
        !          6187:
        !          6188:
        !          6189:  By default, these options are off.  The selected zero axis is drawn
        !          6190:  with a line of type <line_type> and width <line_width> (if supported
        !          6191:  by the terminal driver currently in use), or a user-defined style
        !          6192:  <line_style>.
        !          6193:
        !          6194:  If no linetype is specified, any zero axes selected will be drawn
        !          6195:  using the axis linetype (linetype 0).
        !          6196:
        !          6197:  `set zeroaxis l` is equivalent to `set xzeroaxis l; set yzeroaxis l`. `set
        !          6198:  nozeroaxis` is equivalent to `set noxzeroaxis; set noyzeroaxis`.
        !          6199: 3 zlabel
        !          6200: ?commands set zlabel
        !          6201: ?commands show zlabel
        !          6202: ?set zlabel
        !          6203: ?show zlabel
        !          6204: ?zlabel
        !          6205:  This command sets the label for the z axis.  Please see `set xlabel`.
        !          6206: 3 zmtics
        !          6207: ?commands set zmtics
        !          6208: ?commands set nozmtics
        !          6209: ?commands show zmtics
        !          6210: ?set zmtics
        !          6211: ?set nozmtics
        !          6212: ?show zmtics
        !          6213: ?zmtics
        !          6214: ?nozmtics
        !          6215:  The `set zmtics` command changes tics on the z axis to months of the year.
        !          6216:  Please see `set xmtics` for details.
        !          6217: 3 zrange
        !          6218: ?commands set zrange
        !          6219: ?commands show zrange
        !          6220: ?set zrange
        !          6221: ?show zrange
        !          6222: ?zrange
        !          6223:  The `set zrange` command sets the range that will be displayed on the z axis.
        !          6224:  The zrange is used only by `splot` and is ignored by `plot`.  Please see `set
        !          6225:  xrange` for details.
        !          6226: 3 ztics
        !          6227: ?commands set ztics
        !          6228: ?commands set noztics
        !          6229: ?commands show ztics
        !          6230: ?set ztics
        !          6231: ?set noztics
        !          6232: ?show ztics
        !          6233: ?ztics
        !          6234: ?noztics
        !          6235:  The `set ztics` command controls major (labelled) tics on the z axis.
        !          6236:  Please see `set xtics` for details.
        !          6237: 2 shell
        !          6238: ?commands shell
        !          6239: ?shell
        !          6240:  The `shell` command spawns an interactive shell.  To return to `gnuplot`,
        !          6241:  type `logout` if using VMS, `exit` or the END-OF-FILE character if using
        !          6242:  Unix, `endcli` if using AmigaOS, or `exit` if using MS-DOS or OS/2.
        !          6243:
        !          6244:  A single shell command may be spawned by preceding it with the ! character
        !          6245:  ($ if using VMS) at the beginning of a command line.  Control will return
        !          6246:  immediately to `gnuplot` after this command is executed.  For example, in
        !          6247:  Unix, AmigaOS, MS-DOS or OS/2,
        !          6248:
        !          6249:        ! dir
        !          6250:
        !          6251:  prints a directory listing and then returns to `gnuplot`.
        !          6252:
        !          6253:  On an Atari, the `!` command first checks whether a shell is already loaded
        !          6254:  and uses it, if available.  This is practical if `gnuplot` is run from
        !          6255:  `gulam`, for example.
        !          6256: 2 splot
        !          6257: ?commands splot
        !          6258: ?splot
        !          6259:  `splot` is the command for drawing 3-d plots (well, actually projections on
        !          6260:  a 2-d surface, but you knew that).  It can create a plot from functions or
        !          6261:  a data file in a manner very similar to the `plot` command.
        !          6262:
        !          6263:  See `plot` for features common to the `plot` command; only differences are
        !          6264:  discussed in detail here.  Note specifically that the `binary` and `matrix`
        !          6265:  options (discussed under "datafile-modifiers") are not available for `plot`.
        !          6266:
        !          6267:  Syntax:
        !          6268:        splot {<ranges>}
        !          6269:              <function> | "<datafile>" {datafile-modifiers}}
        !          6270:              {<title-spec>} {with <style>}
        !          6271:              {, {definitions,} <function> ...}
        !          6272:
        !          6273:  where either a <function> or the name of a data file enclosed in quotes is
        !          6274:  supplied.  The function can be a mathematical expression, or a triple of
        !          6275:  mathematical expressions in parametric mode.
        !          6276:
        !          6277:  By default `splot` draws the xy plane completely below the plotted data.
        !          6278:  The offset between the lowest ztic and the xy plane can be changed by `set
        !          6279:  ticslevel`.  The orientation of a `splot` projection is controlled by
        !          6280:  `set view`.  See `set view` and `set ticslevel` for more information.
        !          6281:
        !          6282:  The syntax for setting ranges on the `splot` command is the same as for
        !          6283:  `plot`.  In non-parametric mode, the order in which ranges must be given is
        !          6284:  `xrange`, `yrange`, and `zrange`.  In parametric mode, the order is `urange`,
        !          6285:  `vrange`, `xrange`, `yrange`, and `zrange`.
        !          6286:
        !          6287:  The `title` option is the same as in `plot`.  The operation of `with` is also
        !          6288:  the same as in `plot`, except that the plotting styles available to `splot`
        !          6289:  are limited to `lines`, `points`, `linespoints`, `dots`, and `impulses`;  the
        !          6290:  error-bar capabilities of `plot` are not available for `splot`.
        !          6291:
        !          6292:  The datafile options have more differences.
        !          6293: 3 data-file
        !          6294: ?commands splot datafile
        !          6295: ?splot datafile
        !          6296: ?splot data-file
        !          6297:  As for `plot`, discrete data contained in a file can be displayed by
        !          6298:  specifying the name of the data file, enclosed in quotes,  on the `splot`
        !          6299:  command line.
        !          6300:
        !          6301:  Syntax:
        !          6302:        splot '<file_name>' {binary | matrix}
        !          6303:                            {index <index list>}
        !          6304:                            {every <every list>}
        !          6305:                            {using <using list>}
        !          6306:
        !          6307:  The special filenames `""` and `"-"` are permitted, as in `plot`.
        !          6308:
        !          6309:  In brief, `binary` and `matrix` indicate that the the data are in a special
        !          6310:  form, `index` selects which data sets in a multi-data-set file are to be
        !          6311:  plotted, `every` specifies which datalines (subsets) within a single data
        !          6312:  set are to be plotted, and `using` determines how the columns within a single
        !          6313:  record are to be interpreted.
        !          6314:
        !          6315:  The options `index` and `every` behave the same way as with `plot`;  `using`
        !          6316:  does so also, except that the `using` list must provide three entries
        !          6317:  instead of two.
        !          6318:
        !          6319:  The `plot` options `thru` and `smooth` are not available for `splot`, but
        !          6320:  `cntrparams` and `dgrid3d` provide limited smoothing cabilities.
        !          6321:
        !          6322:  Data file organization is essentially the same as for `plot`, except that
        !          6323:  each point is an (x,y,z) triple.  If only a single value is provided, it
        !          6324:  will be used for z, the datablock number will be used for y, and the index
        !          6325:  of the data point in the datablock will be used for x.  If two values are
        !          6326:  provided, `gnuplot` gives you an error message.  Three values are interpreted
        !          6327:  as an (x,y,z) triple.  Additional values are generally used as errors, which
        !          6328:  can be used by `fit`.
        !          6329:
        !          6330:  Single blank records separate datablocks in a `splot` datafile; `splot`
        !          6331:  treats datablocks as the equivalent of function y-isolines.  No line will
        !          6332:  join points separated by a blank record.  If all datablocks contain the same
        !          6333:  number of points, `gnuplot` will draw cross-isolines between datablocks,
        !          6334:  connecting corresponding points.  This is termed "grid data", and is required
        !          6335:  for drawing a surface, for contouring (`set contour`) and hidden-line removal
        !          6336:  (`set hidden3d`). See also `splot grid data`
        !          6337:
        !          6338:  It is no longer necessary to specify `parametric` mode for three-column
        !          6339:  `splot`s.
        !          6340: 4 binary
        !          6341: ?commands splot datafile binary
        !          6342: ?splot datafile binary
        !          6343: ?splot binary
        !          6344: ?data-file binary
        !          6345: ?datafile binary
        !          6346: ?binary
        !          6347: ?binary data
        !          6348: ?binary files
        !          6349:  `splot` can read binary files written with a specific format (and on a
        !          6350:  system with a compatible binary file representation.)
        !          6351:
        !          6352:  In previous versions, `gnuplot` dynamically detected binary data files.  It
        !          6353:  is now necessary to specify the keyword `binary` directly after the filename.
        !          6354:
        !          6355:  Single precision floats are stored in a binary file as follows:
        !          6356:
        !          6357:        <N+1>  <y0>   <y1>   <y2>  ...  <yN>
        !          6358:         <x0> <z0,0> <z0,1> <z0,2> ... <z0,N>
        !          6359:         <x1> <z1,0> <z1,1> <z1,2> ... <z1,N>
        !          6360:          :      :      :      :   ...    :
        !          6361:
        !          6362:  which are converted into triplets:
        !          6363:        <x0> <y0> <z0,0>
        !          6364:        <x0> <y1> <z0,1>
        !          6365:        <x0> <y2> <z0,2>
        !          6366:         :    :     :
        !          6367:        <x0> <yN> <z0,N>
        !          6368:
        !          6369:        <x1> <y0> <z1,0>
        !          6370:        <x1> <y1> <z1,1>
        !          6371:         :    :     :
        !          6372:
        !          6373:  These triplets are then converted into `gnuplot` iso-curves and then
        !          6374:  `gnuplot` proceeds in the usual manner to do the rest of the plotting.
        !          6375:
        !          6376:  A collection of matrix and vector manipulation routines (in C) is provided
        !          6377:  in `binary.c`.  The routine to write binary data is
        !          6378:
        !          6379:        int fwrite_matrix(file,m,nrl,nrl,ncl,nch,row_title,column_title)
        !          6380:
        !          6381:  An example of using these routines is provided in the file `bf_test.c`, which
        !          6382:  generates binary files for the demo file `demo/binary.dem`.
        !          6383:
        !          6384:  The `index` keyword is not supported, since the file format allows only one
        !          6385:  surface per file.  The `every` and `using` filters are supported.  `using`
        !          6386:  operates as if the data were read in the above triplet form.
        !          6387: ^ <a href="http://www.nas.nasa.gov/~woo/gnuplot/binary/binary.html">Binary File Splot Demo.</a>
        !          6388: 4 example datafile
        !          6389: ?commands splot datafile example
        !          6390: ?splot datafile example
        !          6391: ?splot example
        !          6392:  A simple example of plotting a 3-d data file is
        !          6393:
        !          6394:        splot 'datafile.dat'
        !          6395:
        !          6396:  where the file "datafile.dat" might contain:
        !          6397:
        !          6398:        # The valley of the Gnu.
        !          6399:           0 0 10
        !          6400:           0 1 10
        !          6401:           0 2 10
        !          6402:
        !          6403:           1 0 10
        !          6404:           1 1 5
        !          6405:           1 2 10
        !          6406:
        !          6407:           2 0 10
        !          6408:           2 1 1
        !          6409:           2 2 10
        !          6410:
        !          6411:           3 0 10
        !          6412:           3 1 0
        !          6413:           3 2 10
        !          6414:
        !          6415:  Note that "datafile.dat" defines a 4 by 3 grid ( 4 rows of 3 points each ).
        !          6416:  Rows (datablocks) are separated by blank records.
        !          6417:
        !          6418: ^ <img align=bottom src="http://www.nas.nasa.gov/~woo/gnuplot/doc/splot.gif" alt="[splot.gif]" width=640 height=480>
        !          6419:  Note also that the x value is held constant within each dataline.  If you
        !          6420:  instead keep y constant, and plot with hidden-line removal enabled, you will
        !          6421:  find that the surface is drawn 'inside-out'.
        !          6422:
        !          6423:  Actually for grid data it is not necessary to keep the x values constant
        !          6424:  within a datablock, nor is it necessary to keep the same sequence of y
        !          6425:  values.  `gnuplot` requires only that the number of points be the same for
        !          6426:  each datablock.  However since the surface mesh, from which contours are
        !          6427:  derived, connects sequentially corresponding points, the effect of an
        !          6428:  irregular grid on a surface plot is unpredictable and should be examined
        !          6429:  on a case-by-case basis.
        !          6430: 4 matrix
        !          6431: ?commands splot datafile matrix
        !          6432: ?splot datafile matrix
        !          6433: ?splot matrix
        !          6434: ?data-file matrix
        !          6435: ?datafile matrix
        !          6436: ?matrix
        !          6437:  The `matrix` flag indicates that the ASCII data are stored in matrix format.
        !          6438:  The z-values are read in a row at a time, i. e.,
        !          6439:        z11 z12 z13 z14 ...
        !          6440:        z21 z22 z23 z24 ...
        !          6441:        z31 z32 z33 z34 ...
        !          6442:  and so forth.  The row and column indices are used for the x- and y-values.
        !          6443: 3 grid_data
        !          6444: ?commands splot grid_data
        !          6445: ?splot grid_data
        !          6446: ?grid_data
        !          6447:  The 3D routines are designed for points in a grid format, with one sample,
        !          6448:  datapoint, at each mesh intersection; the datapoints may originate from
        !          6449:  either evaluating a function, see `set isosamples`, or reading a datafile,
        !          6450:  see `splot datafile`.  The term "isoline" is applied to the mesh lines for
        !          6451:  both functions and data.  Note that the mesh need not be rectangular in x
        !          6452:  and y, as it may be parameterized in u and v, see `set isosamples`.
        !          6453:
        !          6454:  However, `gnuplot` does not require that format.  In the case of functions,
        !          6455:  'samples' need not be equal to 'isosamples', i.e., not every x-isoline
        !          6456:  sample need intersect a y-isoline. In the case of data files, if there
        !          6457:  are an equal number of scattered data points in each datablock, then
        !          6458:  "isolines" will connect the points in a datablock, and "cross-isolines"
        !          6459:  will connect the corresponding points in each datablock to generate a
        !          6460:  "surface".  In either case, contour and hidden3d modes may give different
        !          6461:  plots than if the points were in the intended format.  Scattered data can be
        !          6462:  converted to a {different} grid format with `set dgrid3d`.
        !          6463:
        !          6464:  The contour code tests for z intensity along a line between a point on a
        !          6465:  y-isoline and the corresponding point in the next y-isoline.  Thus a `splot`
        !          6466:  contour of a surface with samples on the x-isolines that do not coincide with
        !          6467:  a y-isoline intersection will ignore such samples. Try:
        !          6468:         set xrange [-pi/2:pi/2]; set yrange [-pi/2:pi/2]
        !          6469:         set function style lp
        !          6470:         set contour
        !          6471:         set isosamples 10,10; set samples 10,10;
        !          6472:         splot cos(x)*cos(y)
        !          6473:         set samples 4,10; replot
        !          6474:         set samples 10,4; replot
        !          6475:
        !          6476: 3 splot_overview
        !          6477: ?commands splot_overview
        !          6478: ? splot_overview
        !          6479:  `splot` can display a surface as a collection of points, or by connecting
        !          6480:  those points.  As with `plot`, the points may be read from a data file or
        !          6481:  result from evaluation of a function at specified intervals, see `set
        !          6482:  isosamples`.  The surface may be approximated by connecting the points
        !          6483:  with straight line segments, see `set surface`, in which case the surface
        !          6484:  can be made opaque with `set hidden3d.`  The orientation from which the 3d
        !          6485:  surface is viewed can be changed with `set view`.
        !          6486:
        !          6487:  Additionally, for points in a grid format, `splot` can interpolate points
        !          6488:  having a common amplitude (see `set contour`) and can then connect those
        !          6489:  new points to display contour lines, either directly with straight-line
        !          6490:  segments or smoothed lines (see `set cntrparams`).  Functions are already
        !          6491:  evaluated in a grid format, determined by `set isosamples` and `set samples`,
        !          6492:  while file data must either be in a grid format, as described in `data-file`,
        !          6493:  or be used to generate a grid (see `set dgrid3d`).
        !          6494:
        !          6495:  Contour lines may be displayed either on the surface or projected onto the
        !          6496:  base.  The base projections of the contour lines may be written to a
        !          6497:  file, and then read with `plot`, to take advantage of `plot`'s additional
        !          6498:  formatting capabilities.
        !          6499: 2 test
        !          6500: ?commands test
        !          6501: ?test
        !          6502:  `test` creates a display of line and point styles and other useful things
        !          6503:  appropriate for the terminal you are using.
        !          6504:
        !          6505:  Syntax:
        !          6506:        test
        !          6507: 2 update
        !          6508: ?commands update
        !          6509: ?update
        !          6510:  This command writes the current values of the fit parameters into the given
        !          6511:  file, formatted as an initial-value file (as described in the `fit`section).
        !          6512:  This is useful for saving the current values for later use or for restarting
        !          6513:  a converged or stopped fit.
        !          6514:
        !          6515:  Syntax:
        !          6516:        update <filename> {<filename>}
        !          6517:
        !          6518:  If a second filename is supplied, the updated values are written to this
        !          6519:  file, and the original parameter file is left unmodified.
        !          6520:
        !          6521:  Otherwise, if the file already exists, `gnuplot` first renames it by
        !          6522:  appending `.old` and then opens a new file.  That is, "`update 'fred'`"
        !          6523:  behaves the same as "`!rename fred fred.old; update 'fred.old' 'fred'`".
        !          6524:  [On DOS and other systems that use the twelve-character "filename.ext"
        !          6525:  naming convention, "ext" will be "`old`" and "filename" will be related
        !          6526:  (hopefully recognizably) to the initial name.  Renaming is not done at all
        !          6527:  on VMS systems, since they use file-versioning.]
        !          6528:
        !          6529:  Please see `fit` for more information.
        !          6530: 1 Graphical User Interfaces
        !          6531: ?graphical user interfaces
        !          6532: ?gui's
        !          6533:  Several graphical user interfaces have been written for `gnuplot` and one for
        !          6534:  win32 is included in this distribution.  In addition, there is a Macintosh
        !          6535:  interface at
        !          6536: ^<a href="ftp://ftp.ee.gatech.edu/pub/mac/gnuplot">
        !          6537:         ftp://ftp.ee.gatech.edu/pub/mac/gnuplot
        !          6538: ^</a>
        !          6539:  and several X11 interfaces include three Tcl/Tk located at the usual Tcl/Tk
        !          6540:  repositories.
        !          6541: 1 Bugs
        !          6542: ?bugs
        !          6543:  Floating point exceptions (floating point number too large/small, divide by
        !          6544:  zero, etc.) may occasionally be generated by user defined functions.  Some of
        !          6545:  the demos in particular may cause numbers to exceed the floating point range.
        !          6546:  Whether the system ignores such exceptions (in which case `gnuplot` labels
        !          6547:  the corresponding point as undefined) or aborts `gnuplot` depends on the
        !          6548:  compiler/runtime environment.
        !          6549:
        !          6550:  The bessel functions do not work for complex arguments.
        !          6551:
        !          6552:  The gamma function does not work for complex arguments.
        !          6553:
        !          6554:  As of `gnuplot` version 3.7, all development has been done using ANSI C.
        !          6555:  With current operating system, compiler, and library releases, the OS
        !          6556:  specific bugs documented in release 3.5, now relegated to `old_bugs`, may
        !          6557:  no longer be relevant.
        !          6558:
        !          6559:  Bugs reported since the current release may be located via the official
        !          6560:  distribution site:
        !          6561:         ftp://ftp.dartmouth.edu/pub/gnuplot
        !          6562:        http://www.cs.dartmouth.edu/gnuplot_info.html
        !          6563:
        !          6564:  Please e-mail any bugs to bug-gnuplot@dartmouth.edu.
        !          6565: 2 Old_bugs
        !          6566: ?old_bugs
        !          6567: ?os_bugs
        !          6568:  There is a bug in the stdio library for old Sun operating systems (SunOS
        !          6569:  Sys4-3.2).  The "%g" format for 'printf' sometimes incorrectly prints numbers
        !          6570:  (e.g., 200000.0 as "2").  Thus, tic mark labels may be incorrect on a Sun4
        !          6571:  version of `gnuplot`.  A work-around is to rescale the data or use the `set
        !          6572:  format` command to change the tic mark format to "%7.0f" or some other
        !          6573:  appropriate format.  This appears to have been fixed in SunOS 4.0.
        !          6574:
        !          6575:  Another bug: On a Sun3 under SunOS 4.0, and on Sun4's under Sys4-3.2 and
        !          6576:  SunOS 4.0, the 'sscanf' routine incorrectly parses "00 12" with the format
        !          6577:  "%f %f" and reads 0 and 0 instead of 0 and 12.  This affects data input.  If
        !          6578:  the data file contains x coordinates that are zero but are specified like
        !          6579:  '00', '000', etc, then you will read the wrong y values.  Check any data
        !          6580:  files or upgrade the SunOS.  It appears to have been fixed in SunOS 4.1.1.
        !          6581:
        !          6582:  Suns appear to overflow when calculating exp(-x) for large x, so `gnuplot`
        !          6583:  gets an undefined result.  One work-around is to make a user-defined function
        !          6584:  like e(x) = x<-500 ? 0 : exp(x).  This affects plots of Gaussians (exp(-x*x))
        !          6585:  in particular, since x*x grows quite rapidly.
        !          6586:
        !          6587:  Microsoft C 5.1 has a nasty bug associated with the %g format for 'printf'.
        !          6588:  When any of the formats "%.2g", "%.1g", "%.0g", "%.g" are used, 'printf' will
        !          6589:  incorrectly print numbers in the range 1e-4 to 1e-1.  Numbers that should be
        !          6590:  printed in the %e format are incorrectly printed in the %f format, with the
        !          6591:  wrong number of zeros after the decimal point.  To work around this problem,
        !          6592:  use the %e or %f formats explicitly.
        !          6593:
        !          6594:  `gnuplot`, when compiled with Microsoft C, did not work correctly on two VGA
        !          6595:  displays that were tested.  The CGA, EGA and VGA drivers should probably be
        !          6596:  rewritten to use the Microsoft C graphics library.  `gnuplot` compiled with
        !          6597:  Borland C++ uses the Turbo C graphics drivers and does work correctly with
        !          6598:  VGA displays.
        !          6599:
        !          6600:  VAX/VMS 4.7 C compiler release 2.4 also has a poorly implemented %g format
        !          6601:  for 'printf'.  The numbers are printed numerically correct, but may not be in
        !          6602:  the requested format.  The K&R second edition says that for the %g format, %e
        !          6603:  is used if the exponent is less than -4 or greater than or equal to the
        !          6604:  precision.  The VAX uses %e format if the exponent is less than -1.  The VAX
        !          6605:  appears to take no notice of the precision when deciding whether to use %e or
        !          6606:  %f for numbers less than 1.  To work around this problem, use the %e or %f
        !          6607:  formats explicitly.  From the VAX C 2.4 release notes: e,E,f,F,g,G  Result
        !          6608:  will always contain a decimal  point.  For g and G, trailing zeros will not
        !          6609:  be removed from the result.
        !          6610:
        !          6611:  VAX/VMS 5.2 C compiler release 3.0 has a slightly better implemented %g
        !          6612:  format than release 2.4, but not much.  Trailing decimal points are now
        !          6613:  removed, but trailing zeros are still not removed from %g numbers in
        !          6614:  exponential format.
        !          6615:
        !          6616:  The two preceding problems are actually in the libraries rather than in the
        !          6617:  compilers.  Thus the problems will occur whether `gnuplot` is built using
        !          6618:  either the DEC compiler or some other one (e.g. the latest gcc).
        !          6619:
        !          6620:  ULTRIX X11R3 has a bug that causes the X11 driver to display "every other"
        !          6621:  graph.  The bug seems to be fixed in DEC's release of X11R4 so newer releases
        !          6622:  of ULTRIX don't seem to have the problem.  Solutions for older sites include
        !          6623:  upgrading the X11 libraries (from DEC or direct from MIT) or defining
        !          6624:  ULTRIX_KLUDGE when compiling the x11.trm file.  Note that the kludge is not
        !          6625:  an ideal fix, however.
        !          6626:
        !          6627:  The constant HUGE was incorrectly defined in the NeXT OS 2.0 operating
        !          6628:  system.  HUGE should be set to 1e38 in plot.h. This error has been corrected
        !          6629:  in the 2.1 version of NeXT OS.
        !          6630:
        !          6631:  Some older models of HP plotters do not have a page eject command 'PG'.  The
        !          6632:  current HPGL driver uses this command in HPGL_reset.  This may need to be
        !          6633:  removed for these plotters.  The current PCL5 driver uses HPGL/2 for text as
        !          6634:  well as graphics.  This should be modified to use scalable PCL fonts.
        !          6635:
        !          6636:  On the Atari version, it is not possible to send output directly to the
        !          6637:  printer (using `/dev/lp` as output file), since CRs are added to LFs in
        !          6638:  binary output.  As a work-around, write the output to a file and copy it to
        !          6639:  the printer afterwards using a shell command.
        !          6640:
        !          6641:  On AIX 4, the literal 'NaNq' in a datafile causes the special internal value
        !          6642:  'not-a-number' to be stored, rather than setting an internal 'undefined'
        !          6643:  flag.  A workaround is to use `set missing 'NaNq'`.
        !          6644:
        !          6645:  There may be an up-to-date list of bugs since the release on the WWW page:
        !          6646:        http://www.cs.dartmouth.edu/gnuplot_info.html
        !          6647:
        !          6648:  Please report any bugs to bug-gnuplot@dartmouth.edu.

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