>>>>> PIKAL Petr >>>>> on Tue, 13 Nov 2018 08:42:22 +0000 writes:
> Hi > similar result (with different numerical values) could > be achieved by making v a factor. > > v <- letters[c(2,2,1,2,1,1)] > > vf<-factor(v) > > as.numeric(vf) > [1] 2 2 1 2 1 1 > > Cheers > Petr Yes, as was already remarked by Michael Sumner. But really the power is in match() : It is called at *twice* by factor(). Martin > > -----Original Message----- > > From: R-help <r-help-boun...@r-project.org> On Behalf Of Bert Gunter > > Sent: Tuesday, November 13, 2018 6:44 AM > > To: Duncan Murdoch <murdoch.dun...@gmail.com> > > Cc: R-help <R-help@r-project.org> > > Subject: Re: [R] which element is duplicated? > > > > It is not clear to what you want for the general case. Perhaps: > > > > > v <- letters[c(2,2,1,2,1,1)] > > > wh <- tapply(seq_along(v),factor(v), '[',1) w <- wh[match(v,v[wh])] w > > b b a b a a > > 1 1 3 1 3 3 > > > ## and if you want NA's for the first occurences of unique values ## > > > of course: > > > w[wh] <- NA > > > w > > b b a b a a > > NA 1 NA 1 3 3 > > > > I'd like to see a cleverer solution that vectorizes and avoids the tapply(), > > though. > > > > Cheers, > > Bert > > > > > > > > > > On Mon, Nov 12, 2018 at 8:33 PM Bert Gunter <bgunter.4...@gmail.com> > > wrote: > > > > > > match(v, unique(v)) > > > [1] 1 2 2 1 > > > > > > Bert Gunter > > > > > > "The trouble with having an open mind is that people keep coming along > > > and sticking things into it." > > > -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) > > > > > > > > > On Mon, Nov 12, 2018 at 5:08 PM Duncan Murdoch > > > <murdoch.dun...@gmail.com> > > > wrote: > > > > > >> The duplicated() function gives TRUE if an item in a vector (or row > > >> in a matrix, etc.) is a duplicate of an earlier item. But what I > > >> would like to know is which item does it duplicate? > > >> > > >> For example, > > >> > > >> v <- c("a", "b", "b", "a") > > >> duplicated(v) > > >> > > >> returns > > >> > > >> [1] FALSE FALSE TRUE TRUE > > >> > > >> What I want is a fast way to calculate > > >> > > >> [1] NA NA 2 1 > > >> > > >> or (equally useful to me) > > >> > > >> [1] 1 2 2 1 > > >> > > >> The result should have the property that if result[i] == j, then v[i] > > >> == v[j], at least for i != j. > > >> > > >> Does this already exist somewhere, or is it easy to write? > > >> > > >> Duncan Murdoch > > >> > > >> ______________________________________________ > > >> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > > >> 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 -- To UNSUBSCRIBE and more, see 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.