[R] Question about a passage in R language

[Bert Gunter]

I think we need to consult a lawyer on this one ... :-)

?Extract says that an empty index is "most often used" ... . This is a
vague comment on use, **not** an exact specification of what x[] does.

The R language manual appears to be out of date or wrong: it specifies
that "irrelevant" attributes are anything but names and dimnames in
"Only names and in multi-dimensional arrays dim and dimnames
attributes are retained." As you noted, this is false:

> x <- matrix(1:6,3,2)
> x[]
     [,1] [,2]
[1,]    1    4
[2,]    2    5
[3,]    3    6

> attr(x,"fy")<- "funny"
> x
     [,1] [,2]
[1,]    1    4
[2,]    2    5
[3,]    3    6
attr(,"fy")
[1] "funny"

> x[]
     [,1] [,2]
[1,]    1    4
[2,]    2    5
[3,]    3    6
attr(,"fy")
[1] "funny" ## this contradicts the Language definition manual passage above


Cheers,
Bert
Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Fri, Dec 11, 2015 at 1:09 PM, Sébastien Durier
<sdurier.stat at gmail.com> wrote:
> Hello,
>
> In ?Extract, one can read "An empty index selects all values: this is most
> often used to replace all the entries but keep the attributes"
> No example is given but if x a vector I interpret this sentence as "x[]".
> And in fact, all attributes seem to be preserved by this indexing.
> But in the R language manual
> (https://cran.r-project.org/doc/manuals/r-devel/R-lang.html#Indexing-by-vectors),
> the following passage puzzles me : "Empty. The expression x[] returns x, but
> drops “irrelevant” attributes from the result." I must misunderstand
> something because it sounds contradictory with the help page.
>
> Thank you
>
> SD
>
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