[R] curious about dimension of 'apply' output when MARGIN=1

[Gabor Grothendieck]

The reshape package has an idempotent apply, iapply:

> library(reshape)
> iapply(M,1,function(row) row+c(1,2))
     [,1] [,2]
[1,]    2    6
[2,]    3    7
[3,]    4    8

On 1/16/07, Benjamin Tyner <btyner at stat.purdue.edu> wrote:
> Reading the documentation for 'apply', I understand the following is
> working exactly as documented:
>
>  > M<-matrix(1:6,ncol=2)
>  > M
>     [,1] [,2]
> [1,]    1    4
> [2,]    2    5
> [3,]    3    6
>  > apply(M,2,function(column) column+c(1,2,3))
>     [,1] [,2]
> [1,]    2    5
> [2,]    4    7
> [3,]    6    9
>  > apply(M,1,function(row) row+c(1,2))
>     [,1] [,2] [,3]
> [1,]    2    3    4
> [2,]    6    7    8
>
> I'm not proposing any changes or extra arguments to 'apply'. Rather, I'm
> wondering what is the benefit for (or rationale behind) this somewhat
> unintuitive behavior in the case that MARGIN=1.
>
> Thanks,
> Ben
>
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