Subscript indices must either be real positive integers or logicals.

I am implementing hough transform to detect the circle in edge image.

Here is my code:

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EI=imread('Auto3.jpg');
figure,imshow(EI);

EI=im2double(EI);

EIG=rgb2gray(EI);

[CEIG, thresh]=edge(EIG,'canny',[],.5);

[rows, columns]=size(CEIG);
R=[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20];

H=zeros(rows,columns,length(R));
[yIndex, xIndex]=find(CEIG);

for count=1:length(xIndex)
    for r=1:20
        for yz=121:240
            xz=xIndex(count)-sqrt(R(r)^2-(yIndex(count)-yz)^2);
            xz=round(xz);
            if xz >= 1 && xz <= rows
                H(yz,xz,r) = H(yz,xz,r)+1; 
            end
        end
    end
end

-----------------------------------------------------------------

And the error is:

Subscript indices must either be real positive
integers or logicals.

Error in Test (line 23)
                H(yz,xz,r) = H(yz,xz,r)+1;

Answer 1

[Walter Roberson]

At the command line, command

clear all
dbstop if error

and then run the program. If/when it stops, examine the yz, xz, and r values.

Answer 2

[Matt J]

You need to ensure in some way that

 xz=xIndex(count)-sqrt(R(r)^2-(yIndex(count)-yz)^2);

doesn't generate complex values. Using ROUND will not fix that.