Plot a Surface on a circle and annulus

Hello. I need to plot a surface given by the form z=f(x,y) more specifically z=x^2-y^2 on a circle centered in the origin and radius 2 and on an annulus with given radius 1<=r<=3. Can someone help me with this please?

Answer 1

[Roger Stafford]

For the circle (disk) do this:

[T,R] = meshgrid(linspace(0,2*pi,64),linspace(0,2,16));
X = R.*cos(T);
Y = R.*sin(T);
Z = X.^2-Y.^2;
surf(X,Y,Z)

For the annulus, change first line to:

[T,R] = meshgrid(linspace(0,2*pi,64),linspace(1,3,16));