Making part of a column negative depending on another column

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.

[Walter Roberson]

What is the difference between this question and your earlier http://www.mathworks.co.uk/matlabcentral/answers/86609-converting-positives-to-negatives-in-a-column ?

Answer 1

[Jeff E]

b_new = sign(a) .* b