just put na.omit() inside length() if you intend to omit the NA elements of the vector (otherwise you are trying to omit the NA's of the returned value of length() which is a scalar 2):
length(na.omit(sno[a==1 & b==0])) Regards, Yihui -- Yihui Xie <xieyi...@gmail.com> Phone: 515-294-6609 Web: http://yihui.name Department of Statistics, Iowa State University 3211 Snedecor Hall, Ames, IA On Mon, Oct 5, 2009 at 11:51 PM, Viju Moses <vijumo...@gmail.com> wrote: > I'm seeing what looks to me like odd behaviour when I use na.omit on a > simple "length" function, as follows. > >> sno > [1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 > 25 26 27 28 29 30 31 32 33 34 >> a > [1] 0 1 0 0 1 1 0 0 0 0 0 0 0 0 1 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 >> b > [1] 1 1 0 1 1 1 0 0 NA 0 0 0 NA 0 1 NA 0 1 0 0 0 0 NA 0 > 0 0 0 NA 0 NA 0 1 0 0 > > #NA refers to no data available. > >> df=data.frame(sno,a,b) > # I'm pasting the sorted data frame below: >> sortdf=df[order(a,b),] >> sortdf > sno a b > 3 3 0 0 > 7 7 0 0 > 8 8 0 0 > 10 10 0 0 > 11 11 0 0 > 12 12 0 0 > 14 14 0 0 > 17 17 0 0 > 20 20 0 0 > 21 21 0 0 > 22 22 0 0 > 24 24 0 0 > 25 25 0 0 > 26 26 0 0 > 27 27 0 0 > 29 29 0 0 > 31 31 0 0 > 33 33 0 0 > 34 34 0 0 > 1 1 0 1 > 4 4 0 1 > 9 9 0 NA > 13 13 0 NA > 23 23 0 NA > 28 28 0 NA > 30 30 0 NA > 19 19 1 0 > 2 2 1 1 > 5 5 1 1 > 6 6 1 1 > 15 15 1 1 > 18 18 1 1 > 32 32 1 1 > 16 16 1 NA > > #Now I wish to count howmany records have a=1 AND b=0. From the lower > section of that sorted dataframe we see the answer is 1 (record # 19). But > instead I'm seeing 2. Probably counting record # 16 also. > >> na.omit(length(sno[a==1 & b==0])) > [1] 2 > > I'd be grateful to anyone who can point out what I'm doing wrong. > > Regards. > > ______________________________________________ > 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.
