Hi there, this is probably simple but I can't seem to figure it out by myself...
I have two dataframes (df.1 and df.2): df.1 <- data.frame(year=factor(rep(1:3,3)), level=rep(letters[1:3],3), number=c(11:19)) df.2 <- data.frame(year=factor(c(1:5)), number=c(21:25)) I would like to create a new variable df.1$new, which is supposed to be the sum of each element of df.1$number and those elements of df.2$number, where df.2$year equals df.1$year. What would be the most efficient way of doing this? Regards, EH ______________________________________________ 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.
