MATLAB: Multiplication of certain values using logical array

Question

Hi all,

I have a matrix from which I have derived a logical array. What I'd like to do is multiply true values in the original matrix by -1. I can change these values to a constant value but I can't figure out how to multiply the existing value.

I should add that I'm after a vectorisation rather than loops to quicken my script.

thanks in advance,

Rachel

Answer 1

If A is your original matrix and fltr is the derived logical array (having the same dimensions as A), than:

A(fltr) = -A(fltr);

Should do the trick.

(I think Andrei might have misunderstood your question. Or did I?...)