Contour plot using meshgrid

[x,y] = meshgrid(-5:0.1:5,-5:0.1:5);
r = sqrt(x.^2+y.^2);
theta = atan(y/x);
gamma = 2;
B = 2;
u = 1;
psi = u.*r.*sin(theta)-B./r.*sin(theta)-gamma/(2*pi).*log(r);
contour(x,y,psi)

When i run this, the plot is not showing the psi-function. How can that be? What do I have to change?

I get the following warnings:

Line 3: Matrix is singular to working precision

Line 8: Contour is not rendered for non-finite Zdata

Answer 1

[Walter Roberson]

[x,y] = meshgrid(-5:0.1:5,-5:0.1:5);
r = sqrt(x.^2+y.^2);
theta = atan2(y, x);
gamma = 2;
B = 2;
u = 1;
psi = u.*r.*sin(theta)-B./r.*sin(theta)-gamma/(2*pi).*log(r);
contour(x,y,psi)