On 15-02-2012, at 05:17, Redding, Matthew wrote: > Hi All, > > > I've been trawling through the documentation and listserv archives on this > topic -- but > as yet have not found a solution. I'm sure this is pretty simple with R, but > I cannot work out how without > resorting to ugly nested loops. > > As far as I can tell, grep, match, and %in% are not the correct tools. > > Question: > given these vectors -- > patrn <- c(1,2,3,4) > exmpl <- c(3,3,4,2,3,1,2,3,4,8,8,23,1,2,3,4,4,34,4,3,2,1,1,2,3,4) > > how do I get the desired answer by finding the occurence of the pattern and > returning the starting indices: > 6, 13, 23 >
patrn.rev <- rev(patrn) w <- embed(exmpl,length(patrn)) w.pos <- apply(w,1,function(r) all(r == patrn.rev)) which(w.pos) You can substitute the last three lines to get a oneliner. Berend ______________________________________________ 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.
