Rolf Turner wrote:
On 12/11/2008, at 11:29 AM, Peter Dalgaard wrote:
Ben Bolker wrote:
Sometime soon when I have the time and energy I will start
campaigning for an additional "drop" argument to subset that
does what one expects (!!??) with subsetted factor variables ...
Not that one again! For at least one other value of one, the expectation
is the opposite: Factor levels do not go away just because they happen
not to be present in data.
fct <- lapply(dd, is.factor)
dd[fct] <- lapply(dd[fct], "[", drop=TRUE)
and begone with it...
(Don't you mean ``be done with it''?)
I did mean as in "begone with the nuisance", but you're the native
English speaker (to some ixtent, enniwhy...).
(Actually, the last line could have had lapply(dd[fct],factor), I just
got confused about whether in would preserve the level order.)
What would break if subset.default() were changed to:
function (x, subset, drop=FALSE, ...)
{
if (!is.logical(subset))
stop("'subset' must be logical")
x[subset & !is.na(subset),drop=drop]
}
???
Nothing, but Ben wants to fix (as in cat ;-) ) subset.data.frame() and
drop= does otherwise there.
> data.frame(foo=factor(1:2,labels=c("M","F")))[1,,drop=FALSE]
foo
1 M
> data.frame(foo=factor(1:2,labels=c("M","F")))[1,,drop=TRUE]
[1] M
Levels: M F
cheers,
Rolf
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