[R] "[.data.frame" and lapply

[baptiste auguie]

thanks to some off-list replies, I got this to work,


On 25 Mar 2009, at 18:56, baptiste auguie wrote:

> Dear all,
>
>
> Trying to extract a few rows for each element of a list of
> data.frames, I'm puzzled by the following behaviour,
>
>
>> d <- lapply(1:4,  function(i) data.frame(x=rnorm(5), y=rnorm(5)))
>> str(d)
>>
>> lapply(d, "[", i= c(1)) # fine,  this extracts the first columns
>> lapply(d, "[", j= c(1, 3)) # doesn't do nothing ?!


lapply(d, "[", c(1,3),)

I still wonder why the named arguments can't be used here, though.

Thanks all,


baptiste


>>
>> library(plyr)
>>
>> llply(d, "[", j= c(1, 3)) # same
>
>
> Am i misinterpreting the meaning of "j", which I thought was an
> argument of the method "[.data.frame"?
>
>
>> args(`[.data.frame`)
>> function (x, i, j, drop = if (missing(i)) TRUE else length(cols) ==
>>   1)
>>
>
> Many thanks,
>
> baptiste
>
> _____________________________
>
> Baptiste Auguié
>
> School of Physics
> University of Exeter
> Stocker Road,
> Exeter, Devon,
> EX4 4QL, UK
>
> Phone: +44 1392 264187
>
> http://newton.ex.ac.uk/research/emag
>
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_____________________________

Baptiste Auguié

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag