> I faced a similar problem. Here's what I did > > tmp <- > data.frame(A=sample(LETTERS[1:5],10,replace=T),B=sample(letters[1:5],10,replace=T),C=rnorm(10)) > tmp1 <- with(tmp,aggregate(C,list(A=A,B=B),sum)) > tmp2 <- expand.grid(A=sort(unique(tmp$A)),B=sort(unique(tmp$B))) > merge(tmp2,tmp1,all.x=T) > > At least fewer than 10 extra lines of code. Anyone with a simpler solution?
Well, you can almost do this in with the reshape package: tmp <- data.frame(A=sample(LETTERS[1:5],10,replace=T),B=sample(letters[1:5],10,replace=T),C=rnorm(10)) a <- recast(tmp, A + B ~ ., sum) # see also recast(tmp, A ~ B, sum) add.all.combinations(a, row="A", cols = "B") Where add.all.combinations basically does what you outlined above -- it would be easy enough to generalise to multiple dimensions. Hadley ______________________________________________ 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