[R] Why does `[<-.matrix` not exist in base R
pd@|gd @end|ng |rom gm@||@com
Sun Nov 24 15:47:02 CET 2019
The subject is misguided. It is not a problem to assign to a subset of columns.
The issue is that the assignment operation does not want to _expand_ the matrix automatically upon seeing an out-of-bounds index. E.g.:
> M <- matrix(0,2,2)
Error in `[<-`(`*tmp*`, , 3, value = 1) : subscript out of bounds
[1,] 0 1
[2,] 0 1
You can, however, do things like this:
> M <- M[,c(1,2,2)]
[,1] [,2] [,3]
[1,] 0 1 3
[2,] 0 1 3
> On 23 Nov 2019, at 17:58 , David Disabato <ddisab01 using gmail.com> wrote:
> Whenever going from working with a data.frame to a matrix, I get annoyed
> that I cannot assign and subset at the same time with matrices - like I can
> with data.frames.
> For example, if I want to add a new column to a data.frame, I can do
> something like `myDataFrame[, "newColumn"] <- NA`.
> However, with a matrix, this syntax does not work and I have to use a call
> to `cbind` and create a new object. For example, `mymatrix2 <-
> cbind(mymatrix, "newColumn" = NA)`.
> Is there a programming reason that base R does not have a matrix method for
> `[<-` or is it something that arguably should be added?
> David J. Disabato, Ph.D.
> Postdoctoral Research Scholar
> Kent State University
> ddisab01 using gmail.com
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