> -----Original Message----- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of Tim Clark > Sent: Thursday, February 11, 2010 10:53 AM > To: r-help@r-project.org > Subject: Re: [R] Find each time a value changes > > It was brought to my attention that the rle() answer to this > question was not posted. The following gives the correct > answer once the last value is deleted. > > x<-seq(1:100) > y1<-rep(1,10) > y2<-rep(2,10) > y<-c(y1,y2,y1,y1,y1,y2,y1,y2,y1,y2) > xy<-cbind(x,y) > > print(xy) > print(str(xy)) > > # SEE WHAT RLE GIVES > test <- rle(xy[,2]) > print(str(test) > > # USE JIM"S TRICK OF CUMULATIVE SUMMING > # TO GET THE LOCATIONS > result <- cumsum(c(1,rle(xy[,2])$lengths))
This cumsum undoes the diff that rle does. You could do what the first half of rle does with isFirstInRun <- function(x)c(TRUE, x[-1]!=x[-length(x)] or isLastInRun <- function(x)c(x[-1]!=x[-length(x)], TRUE) Use as which(isFirstInRun(xy[,2])) > > > > Tim Clark > Department of Zoology > University of Hawaii > > > --- On Wed, 2/10/10, Ben Tupper <ben.bigh...@gmail.com> wrote: > > > From: Ben Tupper <ben.bigh...@gmail.com> > > Subject: Re: [R] Find each time a value changes > > To: r-help@r-project.org > > Cc: "Tim Clark" <mudiver1...@yahoo.com> > > Date: Wednesday, February 10, 2010, 4:16 PM > > Hi, > > > > On Feb 10, 2010, at 8:58 PM, Tim Clark wrote: > > > > > Dear List, > > > > > > I am trying to find each time a value changes in a > > dataset. The > > > numbers are variables for day vs. night values, so > > what I am really > > > getting is the daily sunrise and sunset. > > > > > > A simplified example is the following: > > > > > > x<-seq(1:100) > > > y1<-rep(1,10) > > > y2<-rep(2,10) > > > y<-c(y1,y2,y1,y1,y1,y2,y1,y2,y1,y2) > > > xy<-cbind(x,y) > > > > > > > > > I would like to know each time the numbers change. > > > Correct answer should be: > > > x=1,11,21,51,61,71,81,91 > > > > > > > I think this gets close... > > > > which(diff(y) != 0) > > [1] 10 20 50 60 70 80 90 > > > > You'll need to fiddle to get exactly what you want. > > > > Cheers, > > Ben > > > > > > > > > I would appreciate any help or suggestions. It > > seems like it should > > > be simple but I'm stuck! > > > > > > Thanks, > > > > > > Tim > > > > > > > > > Tim Clark > > > Department of Zoology > > > University of Hawaii > > > > > > > > > > > > > > > ______________________________________________ > > > 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. > > > > > > > > > ______________________________________________ > 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. > ______________________________________________ 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.
