How about: tapply(dat$x1,dat$subject,function(x) cumsum(x)) which gives you a list for each subject.
this can be converted to a vector: do.call("c",tapply(dat$x1,dat$subject,function(x) cumsum(x))) So if your data frame is ordered for your subjects: cbind(your.data.frame,do.call("c",tapply(dat$x1,dat$subject,function(x) cumsum(x)))) Good luck Bart Daniel Malter wrote: > > Hi, > > subject=c(1,1,1,2,2,2) > visit=c(1,2,3,1,2,3) > x1=c(0.5,1.2,0.7,0.4,0.6,0.1) > > cum=NULL #initialize > for(i in 1:length(subject)){ > cum[i]=sum(x1[subject[i]==subject&visit[i]>=visit]) > } > > I am sure there is a way with tapply or similar functions that is > computationally more efficient. But if your dataset is not very large, the > above function does the job very well. > > Cheers, > Daniel > > > ------------------------- > cuncta stricte discussurus > ------------------------- > > -----Ursprüngliche Nachricht----- > Von: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Im > Auftrag von gallon li > Gesendet: Monday, November 24, 2008 2:22 AM > An: r-help > Betreff: [R] count the cumulative for each subject > > I have a data set like the following: > > subject visit x1 > 1 1 0.5 > 1 2 1.2 > 1 3 0.7 > 2 1 0.4 > 2 2 0.6 > 2 3 1.0 > ..... > > where x1 is the interval between the two visits. Now I want to calculate > the > cumulative intervals since the beinging, for example > > subject visit x1 cum > 1 1 0.5 0.5 > 1 2 1.2 0.5+1.2 > 1 3 0.7 0.5+1.2+0.7 > 2 1 0.4 0.4 > 2 2 0.6 0.4+0.6 > 2 3 1.0 0.4+0.6+1.0 > ..... > > is there an easy to generate the last veriable cum? The number of visits > for > each subject may be different. > > I also want to choose a subset which correspond to the last observation of > each subject. I am also wondering if there is a fast way to do so. > > [[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. > > ______________________________________________ > 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. > > -- View this message in context: http://www.nabble.com/count-the-cumulative-for-each-subject-tp20656012p20657233.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.