Hi everyone, I'm struggling with a little problem for a while, and I'm wondering if anyone could help...
I have a dataset (from retailing industry) that indicates which brands are present in a panel of 500 stores, store , brand 1 , B1 1 , B2 1 , B3 2 , B1 2 , B3 3 , B2 3 , B3 3 , B4 I would like to know how many brands are present in each store, I tried: result <- aggregate(MyData$brand , by=list(MyData$store) , nlevels) but I got: Group.1 x 1 , 4 2 , 4 3 , 4 which is not exactly the result I expected I would like to get sthg like: Group.1 x 1 , 3 2 , 2 3 , 3 Looking around, I found I can delete empty levels of factor using: problem.factor <- problem.factor[,drop=TRUE] But this solution isn't handy for me as I have many stores and should make a subset of my data for each store before dropping empty factor I can't either counting the line for each store (N), because the same brand can appear several times in each store (several products for the same brand, and/or several weeks of observation) I used to do this calculation using SAS with: proc freq data = MyData noprint ; by store ; tables brand / out = result ; run ; (the cool thing was I got a database I can merge with MyData) any idea for doing that in R ? Thanks in advance, King Regards, Sylvain Willart, PhD Marketing, IAE Lille, France ______________________________________________ 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.