"Ted Harding" <ted.hard...@manchester.ac.uk> wrote in message news:xfmail.100913104250.ted.hard...@manchester.ac.uk... > On 13-Sep-10 09:19:21, Feng Li wrote: >> Dear R, >> I have a vector, say a = c(1,2,4,5,6,8). Can I generate a vector >> or array (2-by-3-by-3) of this form >> c(1,2,1,2,1,2,4,5,4,5,4,5,6,8,6,8,6,8) >> in which every two elements in "a" have been repeated twice? >> >> I am to stupid today and could not figure this simple question out... >> Many many thanks! >> >> Feng > > A possible solution (somewhat generalisable): > > a <- c(1,2,4,5,6,8) > Reps <- 3 > > pairs <- matrix(a,nrow=2) > as.vector(pairs[,rep(c(1,2,3),each=Reps)]) > # [1] 1 2 1 2 1 2 4 5 4 5 4 5 6 8 6 8 6 8 > > (By the way, you have 3 repetitions but wrote "twice" -- I assume > you meant "thrice" but the above generalises to 2 repetitions ... :) > > Ted. The pedant in me couldn't resist asking: If he'd said "repeated once" would you expect only one occurence of each pair?
Sorry. I'll get my coat.... Keith J ______________________________________________ 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.
