Message-ID: <4B281850.6000708@biostat.ku.dk>
Date: 2009-12-15T23:14:24Z
From: Peter Dalgaard
Subject: split.data.frame
In-Reply-To: <4B27518E.6030209@dbmail.com>
Romain Francois wrote:
> Hello,
>
> I very much enjoy "with" and "subset" semantics for data frames and was
> wondering if we could have something similar with split, basically by
> evaluating the second argument "with" the data frame :
I seem to recall that this idea was considered and rejected when the
current split.data.frame was written (10 years ago!). The main reasons
were that
- it's not really THAT hard to evaluate a single splitting expression
using with() or eval()
- not all applications will have the splitting factor inside the df to
split ( split(df[-1], df[[1]]) for a simple case)
- if you need a computed splitting factor, there's a risk of inadvertent
variable capture. I.e., if you inside a function do
....
grp <- ...whatever...
spl <- split(x, grp)
....
and x has a variable called grp, what do you get?
--
O__ ---- Peter Dalgaard ?ster Farimagsgade 5, Entr.B
c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K
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~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907