[R] Get a copy of a matrix only for TRUE entries of a matching size boolean matrix?

[Ben Bolker]

   In two steps:

result <- matrix(NA_character_,
    nrow=nrow(mat_letters), ncol =ncol(mat_letters))
result[mat_bools] <- mat_letters[mat_bools]

On 2024-05-03 8:47 a.m., DynV Montrealer wrote:
> Is there a way to get a copy of a matrix only for TRUE entries of a
> matching size boolean matrix? For *example*:
>> mat_letters <- matrix(data=c('A', 'B', 'C', 'D'), ncol=2, byrow=TRUE)
>> mat_letters
>       [,1] [,2]
> [1,] "A"  "B"
> [2,] "C"  "D"
>> mat_bools <- matrix(data=c(FALSE, TRUE, TRUE, FALSE), ncol=2, byrow=TRUE)
>> mat_bools
>        [,1]  [,2]
> [1,] FALSE  TRUE
> [2,]  TRUE FALSE
> *Reminder:* The following is only an example ; the solution might look very
> different.
> some_command(mat_letters, mat_bools, false=empty)
>       [,1] [,2]
> [1,] ""  "B"
> [2,] "C"  ""
> some_command(mat_letters, mat_bools, false=na)
>       [,1] [,2]
> [1,] NA  "B"
> [2,] "C"  NA
> 
> Thank you kindly
> 
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> 
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