standar deviation of a matrix (specific elements)

Dear friends

I want to obtain the standar deviation of a square matrix but only off-diagonal elements. anyone could help me?

Thanks!

Answer 1

[Star Strider]

Two ways, both producing the same value:

M = rand(7);                        % Create Data
diagM = nan(1,size(M,1));
M = M + diag(diagM);
Mmean1 = mean(M(:),'omitnan');
Mmean2 = mean(M(~isnan(M(:))));

[juan moreno]

thanks star! but i dont understand. this program produce the standar deviation of a square matrix without diagonal elements? i need sd but only the elements off-the diagonal.

[Star Strider]

Long day. Wrote mean, meant std. This works:

M = rand(7);                        % Create Data
diagM = nan(1,size(M,1));
M = M + diag(diagM);
Mmean1 = std(M(:),'omitnan');
Mmean2 = std(M(~isnan(M(:))));

It sets the diagonal to NaN, then takes the mean of all elements that are not NaN.

[juan moreno]

THANKS! :D

[Star Strider]

My pleasure!

If my Answer solved your problem, please Accept it.