Dear Peter,
--On woensdag 16 juni 2004 17:06 +0200 Peter Dalgaard <[EMAIL PROTECTED]> wrote:
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?Paul Lemmens <[EMAIL PROTECTED]> writes:
Hello!
If I read ?subset, the workings of the argument drop (to me) seem to imply equivalence of A and B (R 1.9.0):
# A dd <- data.frame(rt=rnorm(10), c=factor(gl(2,5))) dd <- subset(dd, c==1) dd$c <- dd$c[, drop=TRUE] table(dd$c)
1 5
# B dd <- data.frame(rt=rnorm(10), c=factor(gl(2,5))) dd <- subset(dd, c==1, drop=TRUE) table(dd$c)
1 2 5 0
So to lose the second level of dd$c, in method B I still need to 'dd$c <- dd$c[, drop=TRUE]', while the manual seems to imply that with the drop argument to subset() this would not be necessary.
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...
Does "will not drop" imply that it cannot be programmed, should not be programmed, or has not been programmed yet?
kind regards, Paul
-- Paul Lemmens NICI, University of Nijmegen ASCII Ribbon Campaign /"\ Montessorilaan 3 (B.01.05) Against HTML Mail \ / NL-6525 HR Nijmegen X The Netherlands / \ Phonenumber +31-24-3612648 Fax +31-24-3616066
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