[R] subset(..., drop=TRUE) doesn't seem to work.

[Peter Dalgaard]

Paul Lemmens <P.Lemmens at nici.kun.nl> writes:

> >> Could you comment?
> >
> > Looks like a documentation bug. The actual code ends up  doing
> >
> >     x[r, vars, drop = drop]
> >
> > and "[.data.frame" will not drop factor levels. I wonder if it ever
> > did...
> >
> Bottomline: unless I find the time to submit a patch for
> '[.data.frame', I'll need to use the more elaborate way of dropping
> the unused levels?
> 
> Does "will not drop" imply that it cannot be programmed, should not be
> programmed, or has not been programmed yet?

Cannot. The drop argument is doing something different. 

Anyways, the way out is

 d2 <- subset(dd,c==1)
 ifac <- sapply(dd,is.factor)
 d2[ifac] <- lapply(d2[ifac],factor)

or 

 d2 <- subset(dd,c==1)
 d2[] <- lapply(d2, function(x) if (is.factor(x)) factor(x) else x) 



-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
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