MATLAB: Exclude the maximum value per column

matrixmatrix arraymatrix manipulation

Hello,
Consider a matrix 365 x 24.
How can I exclude the maximum value per column?
The final matrix will be 365 x 23 and not contain the maximum value per row.
Thanks.
Pavlos

Best Answer

This will remove the first maximum value from each row:
 >> M = randi(9,6,9)
 M =
   3   9   1   1   1   1   5   2   3
   9   5   2   4   6   3   8   6   4
   3   1   5   8   3   2   7   8   9
   5   6   7   2   1   4   2   9   1
   2   7   3   9   4   2   4   7   8
   4   4   2   2   5   9   8   5   1
 >> R = M.';
 >> [~,row] = max(R,[],1);
 >> col = 1:size(R,2);
 >> idx = sub2ind(size(R),row,col);
 >> N = R(setdiff(1:numel(R),idx));
 >> N = reshape(N,[],size(R,2)).'
 N =
   3   1   1   1   1   5   2   3
   5   2   4   6   3   8   6   4
   3   1   5   8   3   2   7   8
   5   6   7   2   1   4   2   1
   2   7   3   4   2   4   7   8
   4   4   2   2   5   8   5   1
The trick is to remember that MATLAB operates along columns first, so transposing the matrix at the start makes this whole task easier.
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