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." ------------------------------------ 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.
