[datatable-help] Key dropped when DT[, list(a, b)]
Daniel Krizian
daniel.krizian at gmail.com
Fri Nov 22 17:32:26 CET 2013
Hello Steve and thanks for your reply. I am running data.table_1.8.11
Full details below:
> sessionInfo()
R version 3.0.2 (2013-09-25)
Platform: x86_64-w64-mingw32/x64 (64-bit)
locale:
[1] LC_COLLATE=English_United Kingdom.1252 LC_CTYPE=English_United
Kingdom.1252
[3] LC_MONETARY=English_United Kingdom.1252 LC_NUMERIC=C
[5] LC_TIME=English_United Kingdom.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] timeDate_3010.98 data.table_1.8.11 quantstrat_0.7.8
[4] foreach_1.4.1 blotter_0.8.15
PerformanceAnalytics_1.1.1
[7] FinancialInstrument_1.1 quantmod_0.4-0 Defaults_1.1-1
[10] TTR_0.22-0 xts_0.9-5 zoo_1.7-10
loaded via a namespace (and not attached):
[1] codetools_0.2-8 grid_3.0.2 iterators_1.0.6 lattice_0.20-23
plyr_1.8
[6] reshape2_1.2.2 stringr_0.6.2 tools_3.0.2
On Fri, Nov 22, 2013 at 2:45 PM, Steve Lianoglou
<lianoglou.steve at gene.com>wrote:
> Hi Daniel,
>
> On Fri, Nov 22, 2013 at 6:15 AM, daniel.krizian
> <daniel.krizian at gmail.com> wrote:
> > Hello, I have:
> >
> > DT <- data.table(a=1:10, b=1:10,c=1:10, key=c("a","b"))
> > key(DT) # [1] "a" "b"
> > key(DT[,list(a,b)]) # NULL
> >
> > Note that DT loses its key when I select a subset of columns like above.
> >
> > Is this a (known) bug/ expected result?
>
> The key is retained for me when I run your code:
>
> R> key(DT[,list(a,b)])
> [1] "a" "b"
>
> What version of data.table are you using?
>
> -steve
>
> --
> Steve Lianoglou
> Computational Biologist
> Genentech
>
--
*____________________________*
*Daniel Krizian, CFA, CAIA*
T: +44 74 5372 1101
M: daniel.krizian at gmail.com
uk.linkedin.com/in/danielkrizian
B: quantology.wordpress.com
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