You could try: library(plyr) res <- ddply(TestData[,-2],.(ID),numcolwise(max)) colnames(res)[-1] <- paste0(colnames(res)[-1],".max") A.K.
On Friday, June 20, 2014 3:43 PM, Jun Shen <jun.shen...@gmail.com> wrote: Hi all, Here is my situation. I have a dataframe, the structure would be something like this, TestData<-data.frame(ID=rep(1:10,each=10),TIME=rep(seq(0.1,1,0.1),10),VAR1=rnorm(100),VAR2=5*rnorm(100),VAR3=10*rnorm(100)) Basically, I want to extract the maximum value from each ID for VAR1, VAR2, VAR3...... The way I can think of is do.call(rbind,lapply(split(TestData,TestData$ID),function(x)x[which.max(x$VAR1),'VAR1'])) and do this for each of the variables and put the results back. It's kind of clumsy but OK for several variables. I have dozens of them. Is there a better way to do it? It would be ideal to produce the results like ID VAR1.max VAR2.max VAR3.max 1 1.2828796 8.63276 15.051992 2 1.1870067 8.691801 10.736301 3 1.2815352 6.335692 5.827524 4 1.6719411 5.998597 16.646212 5 1.5631107 6.067457 15.331046 6 0.718989 6.610279 7.306005 7 0.8734315 13.39844 16.965365 8 2.7447862 10.21613 22.545131 9 3.490395 10.83543 25.744662 10 0.4719087 11.73021 7.226687 Thanks for any help. Jun Shen [[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.
