I'm very new to matlab so sorry if this is a dumb question. I have to following matrices:

im = imread('image.jpg');  %<370x366 double>
[y,x] = find(im); %x & y both <1280x1 double>
theta;  %<370x366 double> computed from gradient of image

I can currently plot points one at a time like this:

plot(x(502) + 120*cos(theta(y(502),x(502))),y(502) + 120*sin(theta(y(502),x(502))),'*b');

But what I want to do is some how increment an accumulator array, something like this:

acc = zeros(size(im));
acc(y,x) = acc(x + 120*cos(theta(y,x)),y + 120*sin(theta(y,x)),'*b')) + 1;

It would be nice if the 120 could actually be another matrix containing different radius values as well.