[datatable-help] Subsetting with logical

[arun]

Hi M,

Check this link:
http://stackoverflow.com/questions/16191083/subset-data-table-by-logical-column

A.K.

  

On Friday, April 18, 2014 7:53 AM, Michael Smith <my.r.help at gmail.com> wrote:
Hi All,

This is about subsetting using logicals. The code below is
self-explanatory (I hope). Is this a bug or a feature?

Thanks,

M


> DT <- data.table(a = 1:8, b = c(TRUE, FALSE))
> ## This does *not* work, but it should (in my humble opinion).
> DT[b]
Error in eval(expr, envir, enclos) : object 'b' not found
> ## This does work, but seems a bit awkward, given that b is already
> ## logical.
> DT[b == TRUE]
   a    b
1: 1 TRUE
2: 3 TRUE
3: 5 TRUE
4: 7 TRUE
> ## With data.frame things work as expected.
> DF <- as.data.frame(DT)
> DF[DF$b, ]
  a    b
1 1 TRUE
3 3 TRUE
5 5 TRUE
7 7 TRUE
> sessionInfo()
R version 3.0.2 (2013-09-25)
Platform: x86_64-redhat-linux-gnu (64-bit)

locale:
[1] LC_CTYPE=en_US.utf8       LC_NUMERIC=C
LC_TIME=en_US.utf8
[4] LC_COLLATE=en_US.utf8     LC_MONETARY=en_US.utf8
LC_MESSAGES=en_US.utf8
[7] LC_PAPER=en_US.utf8       LC_NAME=C                 LC_ADDRESS=C

[10] LC_TELEPHONE=C            LC_MEASUREMENT=en_US.utf8
LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] data.table_1.9.2 colorout_1.0-1

loaded via a namespace (and not attached):
[1] plyr_1.8.1     Rcpp_0.11.1    reshape2_1.2.2 stringr_0.6.2
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