Thanks for the replies! Obviously I must have used to wrong search terms - sorry.
@greg: I care about the levels after the subset, because if they are not dropped, then they still appear in the subsequent heatmap I make with ggplot (with my read data-set of course). Admittedly I am quite green, and may do things in a rather silly way - but it works (at least I think it does) On 4 September 2010 15:41, Ista Zahn <iz...@psych.rochester.edu> wrote: > Hi Ulrik > > On Sat, Sep 4, 2010 at 12:52 PM, Ulrik Stervbo <ulrik.ster...@gmail.com> > wrote: >> Dear List, >> >> When I subset a data.frame, the levels are not re-adjusted (see >> example). Why is this? Am I missing out on some basic stuff here? > > Only that this issue has come up many times before, and that this list > is archived and searchable. Try > > RSiteSearch("subset drop levels", restrict = c("Rhelp10", "Rhelp08", > "Rhelp02")) > > > -Ista > >> >> Thanks >> Ulrik >> >> >>> m <- data.frame(gender = c("M", "M","F"), ht = c(172, 186.5, 165), wt = >>> c(91,99, 74)) >>> dim(m) >> [1] 3 3 >> >>> levels(m$gender) >> [1] "F" "M" >> >>> s <- subset(m, m$gender == "M") >>> dim(s) >> [1] 2 3 >> >>> levels(s$gender) >> [1] "F" "M" >> >>> cat <- sapply(s, is.factor); s[cat] <- lapply(s[cat], factor) >>> dim(s) >> [1] 2 3 >> >>> levels(s$gender) >> [1] "M" >> >> ______________________________________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> > > > > -- > Ista Zahn > Graduate student > University of Rochester > Department of Clinical and Social Psychology > http://yourpsyche.org > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.