On May 20, 2010, at 6:24 PM, Jonathan wrote: > Thanks, but that doesn't quite work, since I'd want the result of > b[b %in% a] to be symmetric with a[a%in%b] (so if there are two 2's > in EACH vector, I'll get two 2's in the result, but if there are two > 2's in only one vector, but one two in the other, the result will > show only one 2. > > Consider: > > > a <- c(2,4,3) > > b<-c(6,6,5,2,2,8,4) > > > b[b %in% a] > [1] 2 2 4 > > > a[a%in%b] > [1] 2 4 > > The second answer is correct, but I can't predict which variable to > put in which position in the statement, so I'd need them both to be > correct.
Perhaps you should look at something along the lines of : > a <- c(2,4,2,3) > b<-c(6,6,5,2,2,8,4) > a[a %in% b] [1] 2 4 2 > merge(data.frame(table(a)), data.frame(table(b)), by.x="a", by.y="b" ) a Freq.x Freq.y 1 2 2 2 2 4 1 1 And then do a pmin() on the Freq's -- David. > > Best, > Jonathan > > On Thu, May 20, 2010 at 6:10 PM, David Winsemius <dwinsem...@comcast.net > > wrote: > > On May 20, 2010, at 5:58 PM, Jonathan wrote: > > Hi all, > The ?intersect entry kindly points out that it discards duplicate > entries. I'm looking, however, to get the intersection while KEEPING > duplicate entries, and there are no instructions on how to > accomplish this > using intersect(). > > Does anybody have any idea how this might be done, or am I going to > need to > program something from scratch (something like ordering the vectors > and then > looping through them)? > > > > ex: > > a <- c(2,4,2,3) > b<-c(6,6,5,2,2,8,4) > intersect(a,b) > [1] 2 4 > > > b %in% a > [1] FALSE FALSE FALSE TRUE TRUE FALSE TRUE > > # Now use logical indexing on "b" > > > b[b %in% a] > [1] 2 2 4 > > > > > I'd hope the answer to be 2 2 4. > > Regards, > Jonathan > > [[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. > > David Winsemius, MD > West Hartford, CT > > David Winsemius, MD West Hartford, CT [[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.
