Hi, Here's another way: testagg<-aggregate(colnames(test),list(test.ind),function(x) test[,x]) list(unlist(testagg[,2][1]),unlist(testagg[,2][2])) #[[1]] #0.V11 0.V12 0.V13 0.V14 0.V21 0.V22 0.V23 0.V24 1 2 3 4 5 6 7 8
#[[2]] #1.V31 1.V32 1.V33 1.V34 1.V41 1.V42 1.V43 1.V44 1.V51 1.V52 1.V53 1.V54 # 9 10 11 12 13 14 15 16 17 18 19 20 A.K. ----- Original Message ----- From: Rui Barradas <ruipbarra...@sapo.pt> To: Jannis <bt_jan...@yahoo.de> Cc: r-help <r-help@r-project.org> Sent: Tuesday, September 4, 2012 11:30 AM Subject: Re: [R] tapply to data.frame or matrix Hello, Here's a way. test <- as.data.frame(matrix(1:20, ncol = 5, nrow=4)) test.ind <- c(1,1,2,2,2) lapply(split(colnames(test), test.ind), function(x) unlist(test[, x])) Hope this helps, Rui Barradas Em 04-09-2012 15:40, Jannis escreveu: > Dear R users, > > > imagine i have a dataframe and an indexing vector with the length of the > amount of columns of the dataframe. Is there any convenient way to > combine the colums of the dataframe into vectors (or straight away apply > fundtions to these subsets) according to the indexing vector in a > similar manner to the tapply function? > > For example, in the follwoing case, I would like to combine columns 1 > and two into one vector, and columns 3-4 into another: > > test = as.data.frame(matrix(1:20, ncol = 5, nrow=4)) > test.ind =c(1,1,2,2,2) > > > Thanks a lot! > Jannis > > ______________________________________________ > 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.
