[Rd] Small bug in the documentation of `[.data.frame`

[Rui Barradas]

Hello,

Thank you both, Duncan and Martin, for the quick and clear answer.
I hadn't considered printing `[.data.frame`, which is in fact very 
useful, but I had read the Arguments section. What I didn't realize was 
that it was the answer to the question. Sorry for the noise.

Rui Barradas

Às 13:51 de 29/12/20, Martin Maechler escreveu:
>>>>>> Duncan Murdoch
>>>>>>      on Tue, 29 Dec 2020 08:37:51 -0500 writes:
> 
>      > On 29/12/2020 8:29 a.m., Rui Barradas wrote:
>      >> Hello,
>      >>
>      >> R 4.0.3 on Ubuntu 20.10, session info at end.
>      >>
>      >> Isn't the default value of argument drop missing in
>      >>
>      >> ?`[.data.frame`
>      >>
>      >> Usage:
>      >>
>      >> ## S3 method for class 'data.frame'
>      >> x[i, j, drop = ]
>      >>
>      >>
>      >> I had the impression that it was TRUE (it is when running the function,
>      >> I'm talking about the docs).
> 
>      > No, you can see it if you print `[.data.frame`:
> 
>      >> `[.data.frame`
>      > function (x, i, j, drop = if (missing(i)) TRUE else length(cols) ==
>      > 1)
> 
>      > So if you ask for specific rows and your dataframe has more than one
>      > column, it defaults to FALSE.
> 
>      > I think the Rd checks allow you to leave out defaults, but don't allow
>      > you to state them incorrectly, so that's probably why it is left as
>      > blank in the Usage section, and explained in the Arguments section.
> 
>      > Duncan Murdoch
> 
> Yes, indeed, Duncan,  it is as you think (above).
> 
> It is "official" in the sense that we've used this for a long
> time in order to keep the 'Usage' section cleaner, when some
> defaults are sophisticated, and a help page reader should rather
> read the corresponding argument description.
> 
> Martin
> 
> 
>      >> sessionInfo()
>      >> R version 4.0.3 (2020-10-10)
>      >> Platform: x86_64-pc-linux-gnu (64-bit)
>      >> Running under: Ubuntu 20.04.1 LTS
>      >>
>      >> Matrix products: default
>      >> BLAS:   /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.9.0
>      >> LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.9.0
>      >>
>      >> locale:
>      >> [1] LC_CTYPE=pt_PT.UTF-8       LC_NUMERIC=C
>      >> [3] LC_TIME=pt_PT.UTF-8        LC_COLLATE=pt_PT.UTF-8
>      >> [5] LC_MONETARY=pt_PT.UTF-8    LC_MESSAGES=pt_PT.UTF-8
>      >> [7] LC_PAPER=pt_PT.UTF-8       LC_NAME=C
>      >> [9] LC_ADDRESS=C               LC_TELEPHONE=C
>      >> [11] LC_MEASUREMENT=pt_PT.UTF-8 LC_IDENTIFICATION=C
>      >>
>      >> attached base packages:
>      >> [1] stats     graphics  grDevices utils     datasets  methods   base
>      >>
>      >> loaded via a namespace (and not attached):
>      >> [1] compiler_4.0.3 tools_4.0.3
>      >>
>      >>
>      >> Happy holidays,
>      >>
>      >> Rui Barradas
>      >>
>      >> ______________________________________________
>      >> R-devel using r-project.org mailing list
>      >> https://stat.ethz.ch/mailman/listinfo/r-devel
>      >>
> 
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