Hi, is this what you need? b <- c(NA, a[1:length(a)-1]) # shift values of a one step to the right which(a-b == 1)
On Monday 24 May 2010 12:02:55 pm speretti wrote: > Hi, > > I would like to receive help for the following matter: > > If I'm dealing with a numeric vectors containing increasing elements. > i.e. > > a<-c(1,2,2,2,2,3,3,3,4,4,4,5,5,6,7,7,7) > > There exist an efficient way to obtain an vector that indicates the > position of the changing element of "a"? > In this case it would be something like: > > index<-c(1,6,9,12,14,15) > > usually I'm used cycles to obtain boolean vectors of the same length of "a" > indicating the changing elements ...later I've muliplied them for their > numeric sequence and after that I've selected elements different from zero > ...it is quite long... > can you find an easier solution? > > Thank you for you help > -- ---- Friedrich Schuster Dompfaffenweg 6 69123 Heidelberg ______________________________________________ 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.
