do.call(rbind, lapply(split(Votes, Votes$GiverId), function(x){ temp = merge(x, data.frame(VoteCreationDate = 1:6), all = TRUE) temp$GiverId = temp$GiverId[!is.na(temp$GiverId)][1] temp$CumNumUpVotes = cummax(replace(temp$CumNumUpVotes, is.na(temp$CumNumUpVotes), 0)) temp })) # VoteCreationDate GiverId CumNumUpVotes #19.1 1 19 1 #19.2 2 19 1 #19.3 3 19 3 #19.4 4 19 3 #19.5 5 19 7 #19.6 6 19 10 #38.1 1 38 0 #38.2 2 38 0 #38.3 3 38 1 #38.4 4 38 1 #38.5 5 38 2 #38.6 6 38 2

You can look at the built in variable, $psversiontable. If it doesn't exist, you have V1. If it does exist, it will give you all the info you need.

1 > $psversiontable Name Value ---- ----- CLRVersion 2.0.50727.4927 BuildVersion 6.1.7600.16385 PSVersion 2.0 WSManStackVersion 2.0 PSCompatibleVersions {1.0, 2.0} SerializationVersion 1.1.0.1 PSRemotingProtocolVersion 2.1