split.data.frame

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