[R] Conditional Operation in Matrix

[Romildo Martins]

Hello,

I would like to perform the operation a - b, only for the non-zero values.

Thanks a lot!

RMB


> a

 0 0  0  0  4  0  0  0
 0 0  0  0  0  3  0  0
 0 0  0  0  0  0  0  3
 0 0  0  0  0  0  4  0
 0 0  0  0  0  0  0  0
 0 0  0  0  0  0  0  0
 0 0  0  0  0  0  0  0
 0 0  0  0  0  0  0  0

> b

 0 4  4  4  4  4  4  4
 0 0  4  4  4  4  4  4
 0 0  0  4  4  4  4  4
 0 0  0  0  4  4  4  4
 0 0  0  0  0  5  5  5
 0 0  0  0  0  0  5  5
 0 0  0  0  0  0  0  5
 0 0  0  0  0  0  0  0

> a-b (expected)
 0 0  0  0  0  0  0  0
 0 0  0  0  0  -1  0  0
 0 0  0  0  0  0  0  -1
 0 0  0  0  0  0  0  0
 0 0  0  0  0  0  0  0
 0 0  0  0  0  0  0  0
 0 0  0  0  0  0  0  0
 0 0  0  0  0  0  0  0