Hi look to your workspace by ls(). I bet there is some mismatch in variables as your example works for me without any error. You probably redefined sum function.
> test1<-sample(c(0,1),100,replace=T) > test2<-sample(letters,100,replace=T) > aggregate(test1,list(test2),sum) Group.1 x 1 b 1 2 c 3 3 d 1 4 e 4 > sum<-5 > aggregate(test1,list(test2),sum) Error in FUN(X[[1]], ...) : argument "INDEX" is missing, with no default HTH Petr On 8 Dec 2006 at 12:58, Gustaf Rydevik wrote: Date sent: Fri, 8 Dec 2006 12:58:01 +0300 From: "Gustaf Rydevik" <[EMAIL PROTECTED]> To: r-help@stat.math.ethz.ch Subject: [R] Aggregate? > Hi All, > > I think i'm failing to undersatnd how aggregate() is supposed to work. > > example: > > test1<-sample(c(0,1),100,replace=T) > test2<-sample(letters,100,replace=T) > aggregate(test1,list(test2),sum) > Error in data.frame(w, lapply(y, unlist, use.names = FALSE)) : > arguments imply differing number of rows: 26, 0 > > I thought this would give me a list containing the number of ones that > "belong" to each letter. What am I doing wrong? > > Thanks in advance, > > Gustaf > > -- > email:[EMAIL PROTECTED] > tel: +46(0)703051451 > address: Kantorsgatan 50:190 75424 Uppsala Sweden > > ______________________________________________ > R-help@stat.math.ethz.ch 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. Petr Pikal [EMAIL PROTECTED] ______________________________________________ R-help@stat.math.ethz.ch 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.