Great, many thanks to Scott and Petr!
2011/4/27 Petr PIKAL <petr.pi...@precheza.cz>: > Hi > > > r-help-boun...@r-project.org napsal dne 27.04.2011 13:30:13: > >> 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. > > merge(df.1,df.2, by.x="year", by.y="year", all.x=T) > year level number.x number.y > 1 1 a 11 21 > 2 1 a 17 21 > 3 1 a 14 21 > > than you can sum last 2 columns. I believe that sqldf package can do what > you want more efficiently but I do not use it so I do not know exact > syntax. > > Regards > Petr > > >> >> 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. > > ______________________________________________ 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.
