MATLAB: Vector Combination – Matlab Noob

Question

I have two vectors that I want to merge together. Essentially I want to add them together to create another vector R3, but there is one trick. R consists of either positive or negative values or zeros. R2 consists of only 1's and zeros. In the combining, if there is a 1 in R2 in the same row as R the value should be that of R and not R2. Ex.

R =

     0
     0
     0
  -120
     0
     0
     0
     0
    90
     0
     0
     0

R2 =

     1
     1
     0
     1
     0
     0
     0
     1
     0
     0
     0
     0

Desired R3 =

     1
     1
     0
  -120
     0
     0
     0
     1
    90
     0
     0
     0

And NOT R3 =

     1
     1
     0
  -119
     0
     0
     0
     1
    90
     0
     0
     0

Answer 1

   out=R2
 idx=R~=0
 out(idx)=R(idx)