Electric dipole/Code

%--Contour diagram of electric dipole potential field
%  Matlab (R) code.
   close all; clear all

%--Prepare figure properties
   axis([-4 4 -5 5]); axis equal;
   xlabel('x-axis', 'Fonts', 15);
   ylabel('z-axis', 'Fonts', 15);
   set(gca, 'fonts', 14, 'Ytick',  [-4:2: 4] );
   hold on;

%--Negative contours
   cont    = zeros(9,1);
   cont(1) = 0.05;
   step    = 0.02;
   for i=1:9
      cont(i+1) = cont(i) + step;
      step      = step*1.5;
   end
   cont = -100*cont; cont=round(cont); cont=cont/100;

%--x grid
   x = [-3.5 : .05 :  3.5];
%--Negative z-grid
   z = [-5 : .05 :  -.05];

%--Plot below x-axis
   [X Z] = meshgrid(x,z);
   P     = Z./(sqrt(X.^2+Z.^2).^3);  %<--- Function plotted
   [c h] = contour(X,Z,P, cont, 'b' );
   clabel(c,h, 'manual', 'fonts', 12);

%--Flip signs
   z    = -z;
   cont = -cont;

%--Plot above x-axis
   [X Z] = meshgrid(x,z);
   P     = Z./(sqrt(X.^2+Z.^2).^3);  %<--- Function plotted
   [c h] = contour(X,Z,P, cont, 'r');
   clabel(c,h, 'manual', 'fonts', 12);