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 > -----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. > >> > > > > [[alternative HTML version deleted]] > > ______________________________________________ > 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. Osobní údaje: Informace o zpracování a ochraně osobních údajů obchodních partnerů PRECHEZA a.s. jsou zveřejněny na: https://www.precheza.cz/zasady-ochrany-osobnich-udaju/ | Information about processing and protection of business partner’s personal data are available on website: https://www.precheza.cz/en/personal-data-protection-principles/ Důvěrnost: Tento e-mail a jakékoliv k němu připojené dokumenty jsou důvěrné a podléhají tomuto právně závaznému prohláąení o vyloučení odpovědnosti: https://www.precheza.cz/01-dovetek/ | This email and any documents attached to it may be confidential and are subject to the legally binding disclaimer: https://www.precheza.cz/en/01-disclaimer/ ______________________________________________ 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.