[Rd] Subsetting row in single column matrix drops names in resulting vector

[Dmitriy Selivanov]

Emil, thanks for very nice explanation. Wish base drop would have same
behavior as abind::adrop.

чт, 22 нояб. 2018 г., 17:47 Emil Bode emil.bode using dans.knaw.nl:

> The problem is that the drop is only applied (or not) after the
> subsetting, so what R does is:
> - Getting the subset, which means a 1 x 1 matrix.
> - Only then It either returns that as is (when drop=FALSE), or removes ALL
> dimensions of extent 1, regardless of whether these are rows or columns (or
> higher dimensions).
> And it can't keep any names, because what name should be returned? The
> name 'row1' is just as valid as 'col1'.
> I guess if we could design everything anew, a solution would be to be able
> to specify something like a[1,,drop='row'], or a[1,,drop=1] to drop the
> rows but keep columns, and get a vector being equal to 'row1' (which in
> this case just has length-1, and names 'col1')
> That not how it's designed, but you could use 'adrop()' from the 'abind'
> package:
> abind:: adrop(a[1,,drop=FALSE], drop=1) first subsets, then drops the
> row-dimension, so gives what you're looking for.
> Hope this solves your problem.
>
> Best regards,
> Emil Bode
>
>
> On 21/11/2018, 17:58, "R-devel on behalf of Dmitriy Selivanov" <
> r-devel-bounces using r-project.org on behalf of selivanov.dmitriy using gmail.com>
> wrote:
>
>     Hi Rui. Thanks for answer, I'm aware of drop = FALSE option.
> Unfortunately
>     it doesn't resolve the issue - I'm expecting to get a vector, not a
> matrix .
>
>     ср, 21 нояб. 2018 г. в 20:54, Rui Barradas <ruipbarradas using sapo.pt>:
>
>     > Hello,
>     >
>     > Use drop = FALSE.
>     >
>     > a[1, , drop = FALSE]
>     > #     col1
>     > #row1    1
>     >
>     >
>     > Hope this helps,
>     >
>     > Rui Barradas
>     >
>     > Às 16:51 de 21/11/2018, Dmitriy Selivanov escreveu:
>     > > Hello here. I'm struggling to understand R's subsetting behavior in
>     > couple
>     > > of edge cases - subsetting row in a single column matrix and
> subsetting
>     > > column in a single row matrix. I've read R's docs several times and
>     > haven't
>     > > found answer.
>     > >
>     > > Consider following example:
>     > >
>     > > a = matrix(1:2, nrow = 2, dimnames = list(c("row1", "row2"),
> c("col1")))
>     > > a[1, ]
>     > > # 1
>     > >
>     > > It returns *unnamed* vector `1` where I would expect named vector.
> In
>     > fact
>     > > it returns named vector when number of columns is > 1.
>     > > Same issue applicable to single row matrix. Is it a bug? looks very
>     > > counterintuitive.
>     > >
>     > >
>     >
>
>
>     --
>     Regards
>     Dmitriy Selivanov
>
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