I want to change cart to polar !

I want to change cart coordinate to polar system

for example

I read a image file and this value change to double value.

then this array is 3d value

and this chage to polar system

and I want to plot(r,theta) this polar system value ( not polar(r,theta)!!)

I want to see the plot that is plotting linear!!

help about this!

if true
  % clear all;
clc
a=imread('slice.png');
b=double(a);
imagesc(b);
center=b(512,512);
Z=zeros(2000,3);
for r=1:1:512;
  for t=1:1:512;
  x=512+r;
  y=512+t;
  theta=((tan(t/r))^(-1)*180/pi);
  radi=sqrt(r^2+t^2);
  bvalue=b(x,y);
  end
  Z=[Z;radi,theta,bvalue];
end
plot(Z);code
end

Answer 1

[John Petersen]

theta = atan2(t,r)*180/pi;