How do i write a histogram code without the built in functions ?

I want to creat a histogram code, knowing that it'll be counting the number of occurence of 3 values of a pixel.

the idea is i have 3 matrices (L1im, L2im, L3im) representing information extracted from an image, size of each of them is 256*226, and i want to compute how many times a combination of let's say (52,6,40) occures (each number correspends to a matrix/component but they're all of the same pixel)

for i = 1 : 256
    for j = 1 : 256
        for k = 1 : 256
            if  (L1im == i) &  (L2im == j) & (L3im == k)
                myhist(i,j,k)= myhist(i,j,k)+1;
            end
        end
    end
end

can anyone help please ?

Answer 1

[Image Analyst]

That's obviously not correct. Try this 3 dimensional histogram

[L1im, L2im, L3im] = imsplit(rgbImage) % Optionasl, if you want to do this instead of operating on the RGB image directly in the loop
[rows, columns, numberOfColorChannels] = size(rgbImage)
myhist = zeros(256, 256, 256); % histogram for uint8 where gray levels go up to 255
for col = 1 : columns
    for row = 1 : rows
        r = L1im(row, col);
        g = L2im(row, col);
        b = L3im(row, col);
        myhist = myhist(r, g, b) + 1;
    end
end

[nissrine Neyy]

Thank you@Image Analyst for you response, i tryed it and i get this error :

Index in position 1 is invalid. Array indices must be positive integers or logical values.

Error in lbp_pca (line 89)

myhist = myhist(r, g, b) + 1;

how can i fixe it ?