gijo augustin

The loop in the program is not going upto the number of Columns. A modification like this would be more accurate,

for i=1:rnn
    for j=1:cnn
        sums = sum(sum(a(i:i+nn,j:j+nn)));
        sigma(index) = sigma(index) + sums;
        sigma2(index) = sigma2(index) + power(sums,2);
        [n,i,j]

    end
end

where, cnn = cols - nn;