Hi, for one factor, it is enough to do
dat$ageclass <- dat$ageclass[drop=TRUE] the 'purgef' function applies the drop statement for each columns in the data frame and eventually returns a list because that's how 'lapply' works. If you want a data frame in the end, you can either do (as I recall lists also work supplied as data argument, but just to be consistent) dat[] <- lapply(dat, function(x) x[drop=TRUE]) or modify the function as purgef2 <- function(x) as.data.frame(lapply(x, function(x) x[drop = TRUE])) Let's see for example: dat <- data.frame(ageclass=factor(1:2, levels=1:4), sex=factor("male", levels="male")) purgef <- function(x) lapply(x, function(x) x[drop = TRUE]) purgef(dat) $ageclass [1] 1 2 Levels: 1 2 $sex [1] male male Levels: male purgef2(dat) ageclass sex 1 1 male 2 2 male But maybe Ben's update is just enough (it came in as I was writing this reply). Cheers, Peter On Thu, Jan 6, 2011 at 10:16 AM, Jarrett Byrnes <byr...@nceas.ucsb.edu> wrote: > Ah, so, you have factors that are no longer present in the data. I use a > quick function I wrote called purgef to get rid of zombie factors. > > purgef<-function(x) lapply(x, function(x) x[drop = TRUE]) > > > So, here, before your boxplot > > dat$ageclass <- purgef(dat$ageclass) > > On Jan 6, 2011, at 9:09 AM, Howe, Eric (MNR) wrote: > >> Good day list members, >> >> >> >> I was wondering if anyone knows a way to omit specific columns or anova >> cells from boxplots. >> >> >> >> E.g. I produce a boxplot as: >> >> >> >>> boxplot(y ~ ageclass + sex,data=dat) >> >> >> >> where ageclass has 4 levels (including 1-year-old), and sex has 2 >> levels, but the only males included in the analysis are one-year-olds. >> >> The resulting boxplot illustrates differences among age classes of >> females, and between male and female one-year-olds. >> >> However, it has 3 blank columns, corresponding to subadult, young adult, >> and mature age classes of males. >> >> I'd like to exclude those blank columns from the figure. >> >> >> >> Thanks in advance, >> >> >> >> Eric >> >> >> >> >> >> >> [[alternative HTML version deleted]] >> >> _______________________________________________ >> R-sig-ecology mailing list >> R-sig-ecology@r-project.org >> https://stat.ethz.ch/mailman/listinfo/r-sig-ecology > > _______________________________________________ > R-sig-ecology mailing list > R-sig-ecology@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology > > _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology