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Annotation of OpenXM_contrib/gnuplot/demo/vector.dem, Revision 1.1.1.1

1.1       maekawa     1: #
                      2: # This file demonstrates new features in gnuplot 3.6
                      3: # -1- saving contour lines as a gnuplottable file
                      4: # -2- plotting a vector field on the same graph
                      5: # -3- manipulating columns using the '$1,$2' syntax.
                      6: # the example is taken here from Physics is the display of equipotential
                      7: # lines and electrostatic field for a dipole (+q,-q)
                      8: print "\n This file demonstrates new features in gnuplot 3.6"
                      9: print " -1- saving contour lines as a gnuplottable file"
                     10: print " -2- plotting a vector field on the same graph"
                     11: print " -3- manipulating columns using the '$1,$2' syntax."
                     12: print " the example is taken here from Physics is the display of equipotential"
                     13: print " lines and electrostatic field for a dipole (+q,-q)"
                     14: print "\n Please note that this demo runs only on x11 term, because"
                     15: print " It needs to change term to table and then back to screen,"
                     16: print " and gnuplot currently has no way of saving current terminal."
                     17: pause -1 "<CR> to continue"
                     18: #
                     19:       r(x,y)=sqrt(x*x+y*y)
                     20:       v1(x,y)=  q1/(r((x-x0),y))
                     21:       v2(x,y)=  q2/(r((x+x0),y))
                     22: #
                     23:       vtot(x,y)=v1(x,y)+v2(x,y)
                     24: #
                     25:       e1x(x,y)= q1*(x-x0)/r(x-x0,y)**3
                     26:       e1y(x,y)= q1*(y)/r(x-x0,y)**3
                     27:       e2x(x,y)= q2*(x+x0)/r(x+x0,y)**3
                     28:       e2y(x,y)= q2*(y)/r(x+x0,y)**3
                     29:       etotx(x,y)=e1x(x,y)+e2x(x,y)
                     30:       etoty(x,y)=e1y(x,y)+e2y(x,y)
                     31:       enorm(x,y)=sqrt(etotx(x,y)*etotx(x,y)+etoty(x,y)*etoty(x,y))
                     32:       dx1(x,y)=coef*etotx(x,y)/enorm(x,y)
                     33:       dy1(x,y)=coef*etoty(x,y)/enorm(x,y)
                     34:       dx2(x,y)=coef*etotx(x,y)
                     35:       dy2(x,y)=coef*etoty(x,y)
                     36: #
                     37:       coef=.7
                     38:       x0=1.
                     39:       q1=1
                     40:       q2=-1
                     41:       xmin=-10.
                     42:       xmax=10.
                     43:       ymin=-10.
                     44:       ymax=10.
                     45: #
                     46: reset
                     47: set term x11
                     48: set noautoscale
                     49: set xr [xmin:xmax]
                     50: set yr [ymin:ymax]
                     51: set isosam 31,31
                     52: set view 0, 0, 1, 1
                     53: set nosurface
                     54: set contour base
                     55: set cntrparam order 4
                     56: set cntrparam linear
                     57: set cntrparam levels discrete -3,-2 ,-1 ,-0.5 ,-0.2 ,-0.1 ,-0.05 ,-0.02 ,0 ,0.02 ,0.05 ,0.1 ,0.2 ,0.5 ,1 ,2 ,3
                     58: set cntrparam points 5
                     59: #
                     60: set label "-q" at -1,0 center
                     61: set label "+q" at  1,0 center
                     62: splot vtot(x,y) w l
                     63: pause -1 "Now create a file with equipotential lines <CR> to continue"
                     64: set term table
                     65: set out "equipo2.dat"
                     66: rep
                     67: set out
                     68: set term x11
                     69: reset
                     70: plot "equipo2.dat" w l
                     71: pause 0 "Now create a x/y datafile for plotting with vectors "
                     72: pause 0"and display vectors parallel to the electrostatic field"
                     73: pause -1 "<CR> to continue"
                     74: set isosam 31,31
                     75: set term table
                     76: set out "field2xy.dat"
                     77: splot vtot(x,y) w l
                     78: set out
                     79: set term x11
                     80: set noautoscale
                     81: set xr [xmin:xmax]
                     82: set yr [ymin:ymax]
                     83: set isosam 31,31
                     84: plot "field2xy.dat" u 1:2:(coef*dx1($1,$2)):(coef*dy1($1,$2)) w vec, \
                     85: "equipo2.dat" w l
                     86: pause -1 "<CR> to exit"