> On 01 Mar 2016, at 18:33 , David L Carlson <dcarl...@tamu.edu> wrote: > > You need to learn how to send emails in plain text since html gets mangled on > r-help. See your message below. If I understand your question, it has to do > with what happens to factor levels when you subset your data. Subsetting a > factor does not remove empty factor levels. This is documented on the manual > page for subset(): > > "Factors may have empty levels after subsetting; unused levels are not > automatically removed. See droplevels for a way to drop all unused levels > from a data frame." >
Also check ?"[.factor" and the drop=TRUE argument, which allows you to drop unused level from one particular factor. (Yes, there are good reasons that this is not the default.) -pd > ------------------------------------ > David L Carlson > Department of Anthropology > Texas A&M University > College Station, TX 77840-4352 > > > -----Original Message----- > From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of hoda rahmati > via R-help > Sent: Tuesday, March 1, 2016 10:32 AM > To: r-help@r-project.org > Subject: [R] Fw: removing factor values in the main data frame > > Hi all,I have the following main data frame:(mydata) $ TE : num 40 40 > 20 20 20 20 20 20 20 40 ... $ TR : num 49 49 28 28 28 28 28 28 28 49 > ... $ COUNTRY : Factor w/ 27 levels "","AU","BA","BE",..: 8 8 8 8 8 > ...among the COUNTRY I just need US and AU,first I get a subset to contain > just these two countries: > submydata=subset(mydata,COUNTRY%in%c("US","AU")) > factor(submydata$COUNTRY) but after this when I get str of mydata again I > have the same data frame with no changes in COUNTRY, however I want mydata to > be like: > $ TE : num 40 40 20 20 20 20 20 20 20 40 ... $ TR : num 49 49 > 28 28 28 28 28 28 28 49 ... $ COUNTRY : Factor w/ 2 levels > "","AU","US",..: 8 8 8 8 8 8 8 8 8 8Thanks for any help > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Office: A 4.23 Email: pd....@cbs.dk Priv: pda...@gmail.com ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
