Dear Pikal,
Thank you very much for your answer. I think your example is just the problem I have. In the following example you gave to me, > > ff<-factor(letters[1:5]) > > levels(ff[1:2]) > [1] "a" "b" "c" "d" "e" > > fff<-ff[1:2] > > nlevels(fff) > [1] 5 > > > fff > [1] a b > Levels: a b c d e In my understanding, fff is a subset of ff. Why fff's levels is not "a, b" but "a,b,c,d,e". My problem is quite similar to the example. I just want to split the matrix into many subsets and calculate the levels of every subset. Can you tell me how to do? Thank you very much! Best regards, Yichun > -----åå§é®ä»¶----- > å件人: "PIKAL Petr" <petr.pi...@precheza.cz> > åéæ¶é´: 2014å¹´1æ21æ¥ ææäº > æ¶ä»¶äºº: "å¼ ä»¥æ¥" <yczh...@nigpas.ac.cn>, "r-help@r-project.org" > <r-help@r-project.org> > æé: > 主é¢: RE: [R] how to get the numbers of factors in a matrix > > Hi > > It is rather difficult to understand what problem you have. > > post some data e.g. by > > dput(head(bigmatrix)) > > Maybe your problem is in a factor feature that it preserves also empty levels > until you specifically drop them. > > > ff<-factor(letters[1:5]) > > levels(ff[1:2]) > [1] "a" "b" "c" "d" "e" > > fff<-ff[1:2] > > nlevels(fff) > [1] 5 > > > fff > [1] a b > Levels: a b c d e > > Regards > Petr > > > -----Original Message----- > > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > > project.org] On Behalf Of ??? > > Sent: Tuesday, January 21, 2014 7:36 AM > > To: r-help@r-project.org > > Subject: [R] how to get the numbers of factors in a matrix > > > > Dear friends, > > > > > > I have a question do not know how to resolve. > > > > > > I have a big matrix composed of different columns (I use N here). A > > column is "species" and another one is "latitudes". Now, I want to know > > how I can get the number of different "latitudes" for every "species". > > I have tried to split the matrix according to species (X<-split(N, > > N$species) and then use sapply(X, function(m){nlevels(m$latitudes)}) to > > get that. But the result shows the total factor numbers of "latitudes" > > but not the factor numbers of every species I splitted. Also, I have > > tried to use tapply(N$latitudes, N$species, nlevels) to do this. The > > result is the same. I am confused about this. Can someone help me with > > that? Thank you very much! > > > > > > Best regards, > > Yichun > > > > > > > > > > > > > > [[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. > > ________________________________ > Tento e-mail a jakékoliv k nÄmu pÅipojené dokumenty jsou důvÄrné a > jsou urÄeny pouze jeho adresátům. > Jestliže jste obdržel(a) tento e-mail omylem, informujte laskavÄ > neprodlenÄ jeho odesÃlatele. 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