Hi, One method will be: row.names(df1[unlist(tapply(df1$values,df1$groups,FUN=function(x) x==max(x))),]) #[1] "4" "8" "11" #or row.names(df1[as.logical(ave(df1$values,df1$groups,FUN=function(x) x==max(x))),]) #[1] "4" "8" "11" A.K.
----- Original Message ----- From: Omphalodes Verna <omphalodes.ve...@yahoo.com> To: "r-help@r-project.org" <r-help@r-project.org> Cc: Sent: Wednesday, November 7, 2012 1:41 PM Subject: [R] row index for max values of row groups Dear list members! I am looking for ''nice solution'' for (maybe) simple problem. I need a code (small program) to calculate row index for max value (example below: df1$values) by groups (example below: df1$groups). df1 <- data.frame( groups = c(1,1,1,1,1,2,2,2,3,3,3,3), values = c(1,1,1,2,1,1,2,3,2,1,4,3) ) df1 expected results > 4 8 11 # row index of max values by group Thansk to all for help, OV [[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.
