Hi Farnoosh, May be this helps: ?within(DataA,Var3 <- (Var1|Var2)+0) A.K. On Wednesday, March 5, 2014 6:03 PM, farnoosh sheikhi <farnoosh_81 at yahoo.com> wrote: Hi Arun, I have a data like below, I want to collapse var1 and var 2 together. DataA <- read.table(text="ID,Var1,Var2 1,1,0 2,0,1 ? ? ? ? ? ? ? ? ? ? 3,0,0 ? ? ? ? ? ? ? ? ? ? 4,0,1 ? ? ? ? ? ? ? ? ? ? 5,1,0",sep=",",header=TRUE,stringsAsFactors=FALSE) var3 should be a new column (1,1,0,1,1) Thanks tons.