Try this: ave(X, rep(1:(length(X)/2), each = 2), FUN=rev)
On Fri, Jun 27, 2008 at 11:11 AM, David Afshartous < [EMAIL PROTECTED]> wrote: > > All, > > I have a long vector that contains an even number of entries. I'd like to > switch the 1st and 2nd entry, the 3rd and 4th, and so on, without writing a > loop. > > This code works: > > X = c(8, 10, 6, 3, 20, 1) > index = c(2,1,4,3,6,5) > X[index] > > But for a long list is there a way to generate the index? I can get the > parts to the index as: > > index.odd = seq(1,length(X), by = 2) > index.even = index.odd + 1 > > Is there a simple way to interweave them to produce the desired index? Or > is there a better way? > > Cheers, > David > > ______________________________________________ > 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. > -- Henrique Dallazuanna Curitiba-Paraná-Brasil 25° 25' 40" S 49° 16' 22" O [[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.
