Hi > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Raoni Rodrigues > Sent: Tuesday, September 25, 2012 7:22 AM > To: r-help@r-project.org > Subject: [R] Strange data frame behavior > > Hello all, > > I don't understand a strange behavior in data frame manipulation. > > data_frame1 = data.frame(Site = c("S1", "S2", "S3", "S4", "L1", "L2", > "L3", "L4"), > Number = c(1, 3, 5, 2, 1, 1, 2, 1)) > > data_frame2 = data_frame1 [data_frame1$Site != "S1", , drop=T] > > dput (data_frame2) > > structure(list(Site = structure(c(6L, 7L, 8L, 1L, 2L, 3L, 4L), .Label = > c("L1", "L2", "L3", "L4", "S1", "S2", "S3", "S4"), class = "factor"), > Number = structure(c(3L, 4L, 2L, 1L, 1L, 2L, 1L), .Label = c("1", > "2", "3", "5"), class = "factor")), .Names = c("Site", "Number" > ), row.names = 2:8, class = "data.frame") > > Why site "S1" do not disappeared from data_frame2's structure?
Because Site is a factor and its levels are preserved in subset operations. See ?"[" and especially factor part and drop parameter. You can either get rid of factor and change it to character or explicitly call factor to Site variable factor(data_frame2$Site) to get rid of empty levels Regards Petr > > And what I have to do to eliminate it definitively from my new data > frame (data_frame2)? > > Sorry for this basic question, but I really did not understand... > > Thanks in advanced, > > Raoni > -- > Raoni Rosa Rodrigues > Research Associate of Fish Transposition Center CTPeixes Universidade > Federal de Minas Gerais - UFMG Brasil rodrigues.ra...@gmail.com > > ______________________________________________ > 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. ______________________________________________ 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.