# set terminal pngcairo transparent enhanced font "arial,10" fontscale 1.0 size 600, 400 # set output 'vector.1.png' set label 1 "-q" at -1.00000, 0.00000, 0.00000 center norotate back nopoint set label 2 "+q" at 1.00000, 0.00000, 0.00000 center norotate back nopoint set view map scale 1 set isosamples 31, 31 unset surface set contour base set cntrparam levels 17 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 set trange [ -5.00000 : 5.00000 ] noreverse nowriteback set urange [ -5.00000 : 5.00000 ] noreverse nowriteback set vrange [ -5.00000 : 5.00000 ] noreverse nowriteback set xrange [ -10.0000 : 10.0000 ] noreverse nowriteback set x2range [ -10.0000 : 10.0000 ] noreverse nowriteback set yrange [ -10.0000 : 10.0000 ] noreverse nowriteback set y2range [ -10.0000 : 10.0000 ] noreverse nowriteback set zrange [ -10.0000 : 10.0000 ] noreverse nowriteback set cbrange [ -10.0000 : 10.0000 ] noreverse nowriteback set rrange [ 0.00000 : 10.0000 ] noreverse nowriteback set colorbox vertical origin screen 0.9, 0.2 size screen 0.05, 0.6 front noinvert bdefault r(x,y)=sqrt(x*x+y*y) v1(x,y)= q1/(r((x-x0),y)) v2(x,y)= q2/(r((x+x0),y)) vtot(x,y)=v1(x,y)+v2(x,y) e1x(x,y)= q1*(x-x0)/r(x-x0,y)**3 e1y(x,y)= q1*(y)/r(x-x0,y)**3 e2x(x,y)= q2*(x+x0)/r(x+x0,y)**3 e2y(x,y)= q2*(y)/r(x+x0,y)**3 etotx(x,y)=e1x(x,y)+e2x(x,y) etoty(x,y)=e1y(x,y)+e2y(x,y) enorm(x,y)=sqrt(etotx(x,y)*etotx(x,y)+etoty(x,y)*etoty(x,y)) dx1(x,y)=coef*etotx(x,y)/enorm(x,y) dy1(x,y)=coef*etoty(x,y)/enorm(x,y) dx2(x,y)=coef*etotx(x,y) dy2(x,y)=coef*etoty(x,y) NO_ANIMATION = 1 q1 = 1 x0 = 1.0 q2 = -1 coef = 0.7 xmin = -10.0 xmax = 10.0 ymin = -10.0 ymax = 10.0 splot vtot(x,y) w l