Hi Philip, In the decades since you learned R there have been some additions to the language. In particular, R now supports lambda functions. Applying this feature to Ivan's beautiful solution cuts down 7 characters (continuing his golfing analogy)
unlist(lapply(seq_along(x), \(i) x[i] * x[-(1:i)])) Enjoy your return to R! On Tue, Jun 20, 2023 at 8:46 PM Philip Rhoades via R-help < r-help@r-project.org> wrote: > Ivan, > > > On 2023-06-21 03:32, Ivan Krylov wrote: > > В Wed, 21 Jun 2023 03:13:52 +1000 > > Philip Rhoades via R-help <r-help@r-project.org> пишет: > > > >> This: > >> > >> !(1,2,3,4,5) > >> > >> would give this: > >> > >> (2,3,4,5, 6,8,10, 12,15, 20) > > > > Do you mean taking a product of every element of the vector with all > > following vector elements? A relatively straightforward way would be > > (given your vector stored in `x`): > > > > unlist(lapply(seq_along(x), function(i) x[i] * x[-(1:i)])) > > > Perfect! > > > > (I'm sure it could be golfed further.) > > > I will look at Sarah's suggestion too. > > > >> and this: > >> > >> !(1,2,NA,4,5) > >> > >> would give this: > >> > >> (2,4,5, 8,10, 20) > > > > The previous solution seems to give your vector interspersed a bunch of > > NAs, so one way to continue would be to filter it using v[!is.na(v)]. > > > Exactly! > > Thanks people - it would have taken forever to work that out myself (it > has been decades since I looked at R). > > Phil. > -- > Philip Rhoades > > PO Box 896 > Cowra NSW 2794 > Australia > E-mail: p...@pricom.com.au > > ______________________________________________ > 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.
