[datatable-help] there is no package called ‘xts’

[Sam Steingold]

> * Michael Nelson <zvpunry.aryfba at flqarl.rqh.nh> [2013-04-24 00:41:33 +0000]:
>
> frame[, .SD[.N], by = id]

I tried
--8<---------------cut here---------------start------------->8---
dt <- frame[, .SD[1] ,by=id]
--8<---------------cut here---------------end--------------->8---
(I don't care whether I take first or last, see another message).
and I got the note
--8<---------------cut here---------------start------------->8---
Finding groups (bysameorder=TRUE) ... done in 0.121secs. bysameorder=TRUE and o__ is length 0
Optimization is on but j left unchanged as '.SD[1]'
Starting dogroups ... The result of j is a named list. It's very
inefficient to create the same names over and over again for each
group. When j=list(...), any names are detected, removed and put back
after grouping has completed, for efficiency. Using j=transform(), for
example, prevents that speedup (consider changing to :=).
--8<---------------cut here---------------end--------------->8---
and indeed it runs unbelievably slow (as if I were using data.table)

thanks a lot for your detailed reply!

-- 
Sam Steingold (http://sds.podval.org/) on Ubuntu 12.10 (quantal) X 11.0.11300000
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