% Animates the equipotential contours of an electric dipole
%

n = 2*pi;
d = n/50+0.001;
[x,y] = meshgrid(-n:d:n,-n:d:n);
 
nn = 30
j=0;
 
M = moviein(nn);
for j=1:nn
 
z=(x./sqrt(x.^2+y.^2)).^2.*(...
 -sin(sqrt(x.^2+y.^2)-j*2*pi/nn)...
 -cos(sqrt(x.^2+y.^2)-j*2*pi/nn)./sqrt(x.^2+y.^2)...
 );
 
v=[-1 -0.9 -0.8 -0.75 -0.5 -0.25 -0.1 -0.05 0 0.05 0.1 0.25 0.5 ...
0.75 0.8 0.9 1];

%v=[ -0.75 -0.5 -0.25 0 0.25 0.5 0.75 ];
 
contour(z,v);
%contour(z,30);
%colorbar
axis equal
%grid on
 
M(:,j) = getframe;
end

movie(M,5,10)