[R] fusion of two matrices (numerical and logical)

[Vivek Sutradhara]

The result that I want to get is this:
for (i in 1:5) {
  for (j in 1:4) {
    B[i,j] <- ifelse(C[i,j]==FALSE,0,B[i,j])
  }
}
I would like to know if I can do this without loops.

Den lör 5 sep. 2020 kl 20:18 skrev Vivek Sutradhara <viveksutra using gmail.com>:

> Hi
> I would like to get help in combining two matrices. Here is my example:
> A <- 1:20
> B <- matrix(A,nrow=5,ncol=4)
> # B is a numerical matrix
> C <- B<7
> C[4,4] <- TRUE
> # C is a logical matrix
> # if I combine A and C, I get a vector
> D1 <- A[C==TRUE]
> D1
> D2 <- A[C==FALSE]
> D2
>
> I want to get a matrix with the same dimensions as matrix A. At the
> coordinates given by the vector D1, I want to retain the values in
> matrix A. At the locations in D2, I want a zero value.
> I want to know if I can do this without using any loops.
> Thanks, Vivek
>

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