MATLAB: Error using horzcat in a for loop

dimensionserrorfor loophorzcat

Hi everyone, I am testing a for loop and it is showing me some error in the horzcat, I do not know why it does. Can anyone explain me why it happens, and help me to fix my code. Thank you
p=1;
[row,col] = size(A);
for i = 1:row
    for j=1:col
        if(A(i,j)>0)
            z(p,:)=[j,i];
            p=p+1;
        end
    end
end
B=[(1:p-1)',z]
This is the error:
Error in ==> testloop at 11
B=[(1:p-1)',z]
??? Error using ==> horzcat
CAT arguments dimensions are not consistent.
Error in ==> testloop at 11
B=[(1:p-1)',z];

Best Answer

horzcat concatinates arrays in horizontal direction i.e x = [a , b] is horzcat. when you call B=[(1:p-1)' ,z] your are calling horzcat (there is also a version called vertcat).
The problem is that (1:p-1)' and z does not have the same amount of rows. Which is strange, because your code looks correct. perhaps z allready existed before you ran the code? try adding
clear z;
before your loop.
or
B=[(1:p-1)' , z(1:p-1,:)];
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