MATLAB: Standard deviation ignoring 0s in matrix

deviationstandard

Hi all, I have a 295×34 matrix called Absy. I want to take the standard deviation of all the columns, however some columns contain many zeros. I want to ignore the zeros and take the standard deviation (as zeros are only their due to some columns being different size).

Thank you.

Best Answer

One easy way would be to convert all zeros to NaN, and then use the nanstd function to ignore the NaNs in the std calculation.

Absy(Absy==0)=NaN;
s = nanstd(Absy,[],1);   %column by column std deviation

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MATLAB: Standard deviation of non-zero elements of columns of a matrix

Here is a straightforward way.

% Some input data
x = rand(7,6);
x(1,1) = 0; % Put in a couple zeros by hand
x(6,5) = 0;
% Preallocate the array that will hold the standard deviations
sd = zeros(1,6);
% Calculate and store the standard deviations of the non-zero elements.
for nc = 1:6
  indexToNonZero = x(:,nc)~=0;
  sd(nc) = std(x(indexToNonZero,nc));
end

MATLAB: Correlation between two row matrices

Like that, each value of "a" is correlated to each value of "b", but applying the formula of the correlation, the correlation of two single numbers is NaN. To compute the correlation correctly, traspose the input vectors

result  = corr(a', b');

Best Answer

Related Solutions

MATLAB: Standard deviation of non-zero elements of columns of a matrix

MATLAB: Correlation between two row matrices

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