Making part of a column negative depending on another column

Question

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Hello,

I am trying to do the following. I have two column vectors as follows:

 a=[3;5;8;2;-2;-5;-8];
 b=[1;2;3;4;5;6;7];

I am trying to make the values of b corresponding to the locations of a negative in a, negative. so the result would be

b_new=[1;2;3;4;-5;-6;-7]

The last three values of b would be changed to negative because the last three values of a are negative. Both column vectors are the same length.

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Walter Roberson 2013-9-11

Answer 1

Jeff E 2013-9-10

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b_new = sign(a) .* b