Hi, Maybe this is a trivial question but I can not figure out a good solution.
I have a data frame fa and want to add a new column "sum" with the sum value of fa$X1 grouped by fa$X3. > fa X1 X2 X3 1 1 11 1 2 2 12 1 3 3 13 1 4 4 14 2 5 5 15 2 6 6 16 2 7 7 17 3 8 8 18 3 9 9 19 3 10 10 20 3 fa$X3 is the index of group i can >aggregate(fa[,"X1"],list(fa$X3),sum) Group.1 x 1 1 6 2 2 15 3 3 34 then I want to add a new column "sum" in fa and assign the aggregated result to the new column. Is there a solution without using loops? or maybe there is some way can even avoid aggregate operation? Thanks. ______________________________________________ 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.
