Hello Group, I need a modification in the data.table example to get my intended result shown below ... is there a more simple way!
dt <- data.table(A = rep(1:3, each=4), B = rep(1:4, each=3), C = rep(1:2, 6)) dt[, transform(.SD,D=mean(A)), by="B"] The result I want is below ... which is probably long winded! data.table(unique(as.data.frame(dt[, transform(.SD,D=mean(A)), by="B"][,list(B,D)]))) B D [1,] 1 1.000000 [2,] 2 1.666667 [3,] 3 2.333333 [4,] 4 3.000000 Thank you. ______________________________________________ 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.