[R] Unexpected/undocumented behavior of 'within': dropping variable names that start with '.'

[Hadley Wickham]

The problem is that within.data.frame calls as.list.environment with
the default value of all.names = FALSE. I doubt this is a deliberate
feature, and is more likely to be a minor oversight.

Hadley

On Sun, Sep 20, 2015 at 11:49 AM, Brian <zenlines at gmail.com> wrote:
> Dear List,
>
> Somewhere I missed something, and now I'm really missing something!
>
>> d.f <- data.frame(.id = c(TRUE, FALSE, TRUE), dummy = c(1, 2, 3), a =
> c(1, 2, 3), b = c(1, 2, 3) + 1)
>  > within(d.f, {d = a + b})
>    dummy a b d
>  1     1 1 2 3
>  2     2 2 3 5
>  3     3 3 4 7
>  > d.f <- data.frame(.id = c(TRUE, FALSE, TRUE), .dummy = c(1, 2, 3), a
> = c(1, 2, 3), b = c(1, 2, 3) + 1)
>  > within(d.f, {d = a + b})
>    a b d
>  1 1 2 3
>  2 2 3 5
>  3 3 4 7
>
> Could somebody please explain to me why this does this? I think could be
> considered a feature (for lots of calculations within a data frame you
> don't have to remove all extra variables at the end).  I just wish it
> was documented.
>
> Cheers,
> Brian
>
>
> sessionInfo()
>  R version 3.1.0 (2014-04-10)
>  Platform: x86_64-pc-linux-gnu (64-bit)
>
>  locale:
>   [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
>   [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
>   [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
>   [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
>   [9] LC_ADDRESS=C               LC_TELEPHONE=C
>  [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
>
>  attached base packages:
>  [1] splines   grid      stats     graphics  grDevices utils     datasets
>  [8] methods   base
>
>  other attached packages:
>   [1] scales_0.2.4       plyr_1.8.3         reshape2_1.4
> ccchDataProc_0.7
>   [5] ccchTools_0.6      xtable_1.7-4       tables_0.7.79      Hmisc_3.14-5
>   [9] Formula_1.1-2      survival_2.37-7    ggplot2_1.0.1
> IDPmisc_1.1.17
>  [13] lattice_0.20-29    myRplots_1.1       myRtools_1.2       meteoconv_0.1
>  [17] pixmap_0.4-11      RColorBrewer_1.0-5 maptools_0.8-30    sp_1.1-1
>  [21] mapdata_2.2-3      mapproj_1.2-2      maps_2.3-9         chron_2.3-45
>  [25] MASS_7.3-35
>
>  loaded via a namespace (and not attached):
>   [1] acepack_1.3-3.3     cluster_1.15.2      colorspace_1.2-4
>   [4] compiler_3.1.0      data.table_1.9.4    digest_0.6.4
>   [7] foreign_0.8-61      gtable_0.1.2        labeling_0.3
>  [10] latticeExtra_0.6-26 munsell_0.4.2       nnet_7.3-8
>  [13] proto_0.3-10        Rcpp_0.12.0         rpart_4.1-8
>  [16] stringr_0.6.2       tools_3.1.0
>  > within
>  function (data, expr, ...)
>  UseMethod("within")
>  <bytecode: 0x26d32c8>
>  <environment: namespace:base>
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.



-- 
http://had.co.nz/