matrix comparison and substitute value

Hi, I have one matrix

A=[4 2 3

9 5 6]

I have another vector b=[1 0]. I want to compare the first column of A with b, and if the position in A correspondes to a 1 in b, then I would like to replace that value (4 multiply 0.99) and if 0, it will keep as it is . I was wondering is there any way to do that without executing nested for loops?TIA

Answer 1

[Walter Roberson]

A = A * (1 - 0.01 * (repmat(b.', 1, size(A,2)) == 1))