Dear Duncan,
you are right. In both R 2.2.0 and 2.1.1 you get the same result. What has
actually changed is the following:
In R 2.1.1
> mat[1, , drop = FALSE][1]
r1
1
While in R 2.2.0
> mat[1, , drop = FALSE][1]
[1] 1
In both cases
> mat[1, , drop = FALSE]
c1 c2 c3
r1 1 4 7
I would strongly prefer to retain the row index r1 above.
Of course, you could argue that mat[1, , drop = FALSE][1] relates to the
column name c1. However, I think the lower dimension is a vector and this
typically a column with row names. Most likely, a wiser and more concise
interpretation than the mine is necessary, but the problem of dropping and
loosing information is quite evident in any case.
Still, I believe, my suggestion below is justified. Things like this
happen quite often to me and it regularly takes time and effort to rectify
the problem.
Retaining the matrix features in sames could really be an advantage and
avoid many if's and other workarounds.
Many thanks and best regards,
Stefan
Duncan Murdoch <[EMAIL PROTECTED]>
2005-10-18 14:33
An
[EMAIL PROTECTED]
Kopie
r-devel@stat.math.ethz.ch, [EMAIL PROTECTED]
Thema
Re: [Rd] Inconsistency with matrix indexing (PR#8214)
[EMAIL PROTECTED] wrote:
> Full_Name: Stefan Albrecht
> Version: 2.2.0
> OS: Windows XP
> Submission from: (NULL) (194.127.2.74)
>
>
> Dear all,
>
> in the new R 2.2.0, the matrix indexing has been changed.
I just tried your code in R 2.0.1 and 2.1.1, and got the same output as
you did. Which version are you comparing to?
Duncan Murdoch
In my opinion, this
> leads to an inconsistency when indexing one-row matrices.
> Take
>
>>(mat <- matrix(1:9, nrow = 3, dimnames = list(paste("r", 1:3, sep = ""),
>
> paste("c", 1:3, sep = ""))))
> c1 c2 c3
> r1 1 4 7
> r2 2 5 8
> r3 3 6 9
>
> Now taking the first row of the first-row of mat preserves the column
names
>
>>mat[1, , drop = FALSE][1, ]
>
> c1 c2 c3
> 1 4 7
>
> This is not true for the first column of the first-row of mat
>
>>mat[1, , drop = FALSE][, 1]
>
> [1] 1
>
> However, for the first column of the first two rows of mat the row names
are
> retained
>
>>mat[1:2, , drop = FALSE][, 1]
>
> r1 r2
> 1 2
>
> This feature can lead to problems when indexing matrixes of different
row
> numbers, since the row names are not preserved in all cases.
>
> I suggest to preseve the row names also for
>
>>mat[1, , drop = FALSE][, 1]
>
>
> Would it be possible to implement this feature? Many thanks.
>
> With best regards,
>
> Stefan Albrecht
>
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