[R] question about split

[Dimitris Rizopoulos]

try this:

dat <- data.frame(x = runif(100),
     fac1 = rep(c("a", "b", "c", "d"), each = 25),
     fac2 = rep(c("A", "B"), 50))

splits <- c("fac1", "fac2")
split(dat, dat[splits])


I hope it helps.

Best,
Dimitris


On 6/17/2011 2:34 PM, carslaw wrote:
> Dear R-users
>
> I seem to be stumped on something simple.  I want to split a data frame
> by factor levels given in one or more columns e.g. given
>
> dat<- data.frame(x = runif(100),
>                    fac1 = rep(c("a", "b", "c", "d"), each = 25),
>                    fac2 = rep(c("A", "B"), 50))
>
> I know I can split it by fac1, fac2 by:
>
> split(dat, list(dat$fac1, dat$fac2))
>
> which gives a list of length 8 - as desired.
>
> My question is, given a vector of column name(s) to split by, how can I
> supply
> split with these? I was thinking something like:
>
> splits<- c("fac1", "fac2")
> split(dat, list(splits))
>
> But that is clearly wrong....and I can't see the solution
>
> Many thanks
>
> David Carslaw
>
> Science Policy Group
> Environmental Research Group
> MRC-HPA Centre for Environment and Health
> King's College London
> Room 4.129 Franklin Wilkins Building
> Stamford Street
> London SE1 9NH
>
>
>
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-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
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