[datatable-help] Odd behavior with [.data.table and J

Christian Hudon chudon at planora.com
Fri Aug 3 17:34:44 CEST 2012


I'm running into an odd behavior with data.table. Given the following

> tbl = data.table(foo=c(1,2,3), bar=c(1.1, 2.2, 3.3))
> setkey(tbl, foo)
> i = data.frame(foo=1)

... I would expect the following three ways of indexing "tbl" using "i" to
give the same result, but they don't:

> tbl[i]
   foo bar
1:   1 1.1
> tbl[J(i)]
Error in `[.data.table`(tbl, J(i)) :
  typeof x.foo (double) != typeof i.V1 (list)
> tbl[data.table(i)]
   foo bar
1:   1 1.1

Anything I'm missing on why tbl[J(i)] wouldn't work like the other two? Or
have I hit a bug? I'm running R 2.15.1 64bit on Windows 7, with data.table


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