How to normalize rows of a matrix?

Question

Kimberly Cardillo 2020-8-19

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回答： Steven Lord 2020-8-19

I have a matrix called aefm_1 that is 184 x 5119 where each row indicates a signal vector and each column is a time step and each value in the signal vector indicates amplitude at that time step. I want to write a loop that normalizes each signal vector in the matrix from -1 to 1 based on the maximum amplitude for each row. When I try to use the code below, it outputs only a singal vector of dimensions 1 x 5119. In the end, I want an output that is still 184 x 5119. How do I do that?

for i=1:size(aefm_1,1)

aefm_2 = aefm_1(i,:)./max(abs(aefm_1(i,:)));

end

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Answer 1

Geoff Hayes 2020-8-19

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Kimberley - your code is overwriting the value that was assigned to aefm_2 on the previous iteration

aefm_2 = aefm_1(i,:)./max(abs(aefm_1(i,:)));

You will need to set this variable to be an array with the same dimensions as aefm_1 and then update each row of it. Alternatively, you could probably do this in a single line of code without a loop.

aefm_2 = aefm_1 ./ max(abs(aefm_1), [], 2);

See here for why we add the [] and 2 paramaters as inputs to max.