I have a data frame and one separate vector that is a grouping variable for the data frame. I would like to take all rows of the data frame belonging to each group and then sum the columns with out using a for statement.
Something like: take all rows of group 1 then apply(group1.data,1,sum), but do this without having to do it separately for each group. Any ideas? thank you. Dan ______________________________________________ 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.
