How to draw an polar image under polar coordinate

Hello, I have a problem when drawing a polar image. The problem is like this. I have a matrix A in which a distribution under polar coordinate Z=f(theta,r) is described by its elements Z=f(theta,r)=A(i,j). I want to draw it under polar coordinate like the function image.m for cartesian coordinates.

[Stuart Anderson]

Exactly what I needed. Thanks a lot.

Answer 1

[Walter Roberson]

N = 150;
maxr = 20;
theta = linspace(0, 2*pi, N+1);
r = linspace(0, maxr, N+1);
theta = theta(1:end-1);  %throw away 2*pi since it duplicates 0
r = r(2:end);            %throw away 0 since that's at the center
[THETA, R] = ndgrid(theta, r);
Z = f(THETA,R);
[X, Y] = pol2cart(THETA,R);
surf(X, Y, Z);

anything beyond that is drawing the circles and labeling

[yangyichun yang]

Thanks a lot dude, but may I ask that is there a way not to transfer polar into cartesian to draw it like the function polar.m does in matlab？

[Walter Roberson]

polar.m translates its data to cartesian to do its drawing.

The setup in this code establishes a non-uniform coordinate grid, which surf() is perfectly happy with. surf is not going to place the elements on a rectangular grid: it will put the elements into a circle.

There is no true polar coordinate system in MATLAB. polar.m uses entirely cartesian internally, drawing circles in cartesian coordinates, labeling in cartesian coordinates, transforming the input polar coordinates to cartesian coordinates to draw the lines.

[Walter Roberson]

http://uk.mathworks.com/matlabcentral/answers/96327-how-do-i-display-a-polar-coordinates-image-in-cartesian

[Walter Roberson]

Note: in the days since I posted the above, Mathworks did add polaraxes that is not in cartesian coordinates at any user-visible level, and added polarplot

But there is still no Mathworks-provided polar image function. There are File Exchange contributions for polar images, and there is the surf work-around that I posted above.