That makes sense. Thanks all!
2013/7/24 David Carlson <dcarl...@tamu.edu> > Benchmark is probably a subset from a larger dataframe. R does > not automatically remove empty levels but you can do it: > > set.seed(42) > dataset <- data.frame(Benchmark=factor(sample(LETTERS[1:26], > 50, > replace=TRUE), levels=LETTERS[1:26])) > levels(dataset$Benchmark) > # [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" > "O" "P" "Q" "R" "S" > # [20] "T" "U" "V" "W" "X" "Y" "Z" > dataset$Benchmark <- factor(dataset$Benchmark) > levels(dataset$Benchmark) > # [1] "A" "C" "D" "F" "G" "H" "J" "K" "L" "M" "N" "O" "P" "Q" > "R" "S" "T" "V" "X" > # [20] "Y" "Z" > > There are times when you want to know if certain factor levels > do not appear in a subset of the original data. > > ------------------------------------- > David L Carlson > Associate Professor of Anthropology > Texas A&M University > College Station, TX 77840-4352 > > ----Original Message----- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of Borja > Rivier > Sent: Wednesday, July 24, 2013 8:25 AM > To: r-help@r-project.org > Subject: [R] Levels of a factor > > Hi all, > > I am having a bit of trouble using the levels() function. > I have a factor with many elements, and when I use the > function levels() to > extract the list of unique elements, some of the elements > returned are not > actually in the factor. > > For example I would have this: > > > vector <- dataset$Benchmark > > class(vector) > [1] "factor" > > length(vector) > [1] 35615 > > vector2 <- levels(vector) > > length(which(!(vector2 %in% vector))) > [1] 235 > > Does anyone know how this is possible? > > Many thanks! > > Borja > > [[alternative HTML version deleted]] > > ______________________________________________ > 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. > > [[alternative HTML version deleted]] ______________________________________________ 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.
