[R] lapply not reading arguments from the correct environment

jiho jo.irisson at gmail.com
Fri May 18 19:01:44 CEST 2007

On 2007-May-18  , at 18:21 , Gabor Grothendieck wrote:
> In particular, we can use "[" directly instead of subset.  This is the
> same as your function except for the line marked ### :
> myfun2 <- function() {
>       foo = data.frame(1:10,10:1)
>       foos = list(foo)
>       fooCollumn=2
>       cFoo = lapply(foos, "[", fooCollumn) ###
>       return(cFoo)
> }
> myfun2() # test
> On 5/18/07, Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote:
>> You need to study carefully what the semantics of 'subset' are.  The
>> function body of myfun is not in the evaluation environment.  (The  
>> issue
>> is 'subset', not 'lapply': select is an *expression* and not a  
>> value.)
>> Hint: using subset() programmatically is almost always a mistake.   
>> R's
>> subsetting function is '[': subset is a convenience wrapper.

Thank you very much. Indeed it is much better this way. I got used to  
subset for data.frames because [ does not work with negative named  
arguments while select does. E.g.:
does not work while
works (it eliminates columns named name1 and name 2 from x). But I  
guess in most cases an other syntax can achieve the same thing with  
[, like:
it's just a little less clear.
Thanks again.


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