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multiply all numbers above a threshold in a matrix by n, but only on certain indices, and keep original matrix dimension

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cgenes
cgenes on 15 Apr 2019
Commented: cgenes on 15 Apr 2019
Hi,
I want to multiply all numbers above a threshold in a matrix by n, but only on certain indices, and keep the original matrix dimension
so consider I have a 201x201 matrix, but only want to do my multiplication where y=1:115, I can do something like
matrix = rand(201,201);
matrix(matrix(:, 115) > 0.5) = 0;
which works great; but I want to something like
matrix(matrix(:, 115) > 0.5) = matrix .* 100;
but i can't of course because because the left and right sides have a different number of elements
I know this is super simple but please help me because I have a mind block
I think I need to make a logical mask, or something - but I can't think :-(

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