[Rd] split.data.frame

[Felix Andrews]

I agree, I would definitely appreciate that.

A simpler implementation:

split.data.frame <- function(x, f, drop = FALSE, ...)
{
    ff <- eval(substitute(f), x, parent.frame())
    lapply(split(seq_len(nrow(x)), ff, drop = drop, ...),
function(ind) x[ind, , drop = FALSE])
}


df <- data.frame(x = 1:10, y = rep(1:2, each = 5))
split( df, df$y )
split( df, y )
split( df, x > 3 )


2009/12/15 Romain Francois <romain.francois at dbmail.com>:
> 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 :
>
> split.data.frame
> function(x, f, drop = FALSE, ...){
>        call <- match.call( )
>        fcall <- call( "with", data = call[["x"]], expr = call[["f"]] )
>        ff <- eval( fcall, parent.frame(1) )
>
>        lapply(split(seq_len(nrow(x)), ff, drop = drop, ...), function(ind)
> x[ind, , drop = FALSE])
> }
>
>
>> split( df, y )
> $`1`
>  x y
> 1 1 1
> 2 2 1
> 3 3 1
> 4 4 1
> 5 5 1
>
> $`2`
>    x y
> 6   6 2
> 7   7 2
> 8   8 2
> 9   9 2
> 10 10 2
>
>> split( df, x > 3 )
> $`FALSE`
>  x y
> 1 1 1
> 2 2 1
> 3 3 1
>
> $`TRUE`
>    x y
> 4   4 1
> 5   5 1
> 6   6 2
> 7   7 2
> 8   8 2
> 9   9 2
> 10 10 2
>
>
> Romain
>
> --
> Romain Francois
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-- 
Felix Andrews / 安福立
Postdoctoral Fellow
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Fenner School of Environment and Society [Bldg 48a]
The Australian National University
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