Hi,
I'm having a dataframe 'Subset1' with a number of factor variables and 160 numerical variables Now I want to make sums for all rows that have the same values for the different factor variables, except for the factor variables: VAR1,VAR2,VAR3 who may have the same values. With the formula given below this works great, but in a situation with 15000 rows and 13 factor variables the calculation takes more than 2 minutes. So my question is: Does anyone knows if there exists a faster alternative? Subset1.AGG <- as.data.frame(aggregate(Subset1[,(ncol(Subset1)-159):ncol(Subset1)], list(VAR1 = Subset1$VAR1,VAR2=Subset1$VAR2,VAR3 = Subset1$VAR3), FUN=sum) ) Thank you very much for helping me out, Bert [[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.