Plotting a rectangular matrix into a circle

Question

I have generated a rectangular matrix with the azimouth angle changing with rows and the radius changing as you change column. These are meant to represent the relative velocities experienced by a rotating helicopter blade. This produces a matrix called Vmat. I want to plot this to appears in a circle (representing the rotation of the blade)

So far I have tried

[R,T] = meshgrid(r,az);      

[x,y] = pol2cart(T,R);      

surf(x,y,Vmat(r,az));      

which should produce a contoured surface showing velocity as it changes with azimouth angle and radius but it comes up with dimension errors. I don't mind if it is a 2d contour plot or 3d plot i guess both would be written in a similar way.

Thanks James

Answer 1

The error is in writing Vmat(r,az), presuming that these are actual values of radius and azimuth, not indexes into your radius and azimuth. If you want to take only a subset of Vmat that's a slightly different matter, but this should work:

[R,T] = meshgrid(r,az);  % creates a grid in polar coordinates   
[x,y] = pol2cart(T,R);   % changes those to cartesian for surf
surf(x,y,Vmat);      

Alternatively you could do a contour plot:

h = polar([0 2*pi], [0 max(r)]); % set up polar axes with right scale
delete(h) % remove line
hold on
contour(x,y,Vmat);