Many thanks for your elaborated explaina.
At 2012-01-13 11:34:51,"R. Michael Weylandt" <michael.weyla...@gmail.com> wrote: >As Jorge noted, the fix is to use "%in%": a fuller explanation of why >`==` didn't work is that it implicitly used vector recycling: look at > >with(data, id == c("a", "c")) > >implicitly, this expands to id == c("a","c", "a", "c") to get the >lengths to match. Obviously only the first elements work here. > >But when you had c("a", "d") it expanded to c("a","d", "a", "d") and >you get TRUE for the 1st and 4th slot. This, however, was just a lucky >coincidence. Had you used c("d", "a") there would have been no >matches. > >Anyways, definitely use %in% but hopefully this clarifies things. > >Michael > >On Thu, Jan 12, 2012 at 9:50 PM, Jorge I Velez <jorgeivanve...@gmail.com> >wrote: >> Hi, >> >> Use %in% instead of ==. >> >> HTH, >> Jorge.- >> >> >> On Thu, Jan 12, 2012 at 9:36 PM, ÃÏÐÀ <> wrote: >> >>> Hi all >>> I have a question about "subset" function. >>> >>> >>> > dat >>> id x1 x2 x3 >>> 1 a 1 11 111 >>> 2 b 2 22 222 >>> 3 c 3 33 333 >>> 4 d 4 44 444 >>> >>> >>> > subset(dat,id==c("a","c")) >>> id x1 x2 x3 >>> 1 a 1 11 111 >>> >>> > subset(dat,id==c("a","d")) >>> id x1 x2 x3 >>> 1 a 1 11 111 >>> 4 d 4 44 444 >>> >>> >>> >From the above, if I choose id=a,c, the result is wrong,but if I choose >>> id=a,d, the result is right. >>> >>> >>> What's the reason for it? >>> >>> >>> >>> >>> Many thanks! >>> >>> >>> >>> >>> My best >>> >>> >>> [[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. >> [[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.