how to efficiently update one element in a matrix conditioned on another element

Question

xueqi 2014-3-16

0
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https://ww2.mathworks.cn/matlabcentral/answers/121730-how-to-efficiently-update-one-element-in-a-matrix-conditioned-on-another-element

回答： the cyclist 2014-3-16

Hi,

Do you know how to do this? I have a matrix M=[2,3,2;-1,2,3]. I would like to check in any row, if there is a number is less than 0. If so, I let the second column of that row is equal to -Inf. So in this case, as M(2,1)<0.So I update M as [2,3,2;-1,-Inf,3].

I understand I probably can write a loop to do so. But the problem is I need to deal with a big matrix other than M here, which is only 2*3. I will like to speed up the process. So I would like to know if there is an more efficient way to do so? Could any one help me about this please?