Computing Correlation in graycoprops

Hi everyone,

I was trying to check my calculations with the results provided by graycoprops, however, they don't match.

I don't know what I'm doing wrong, here follows my code:

GLCM_0_norm = GLCM_0 ./ sum (GLCM_0(:)) %for the sum of all elements to be equal to 1, as requested per graycoprops

i=size(GLCM_0_norm,1);
j=size(GLCM_0_norm,2)

for k=1:i
    sum_lines(k)=sum(GLCM_0_norm(k,:))
end

mean_row=mean(sum_lines);
std_row=std(sum_lines);

for l=1:j
    sum_column(k)=sum(GLCM_0_norm(:,l));
end

mean_col=mean(sum_column);
std_col=std(sum_column);


for k=1:i
    for l=1:j
        correlation= [(k-mean_row)*(l-mean_col)*GLCM_0_norm(k,l)]/(std_col*std_row)
    end
end

Correlation_0=sum(correlation(:));

PS- I can't use graycoprops for my assignment.

Thanks!