Hello, Here's an idea:
ifelse(z$c == "a", z$a, z$b) > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] > On Behalf Of Gurpal Kalsi > Sent: Wednesday, October 28, 2009 11:15 AM > To: r-help@r-project.org > Subject: [R] Selecting rows according to a column > > Hi, > > With a data such as: > > z = data.frame(a = 1:5, b=10*a, c = c("a", "a", "b", "b", "b") ) > * a b c* > *1* 10 *a* > *2* 20 *a* > 3 *30* *b* > 4 *40* *b* > 5 *50* *b* > > Can anyone suggest a way to select [1, 2, 30, 40, 50], > ie. using column "c" to specify which column is selected for each row. > > Many thanks > > G > > [[alternative HTML version deleted]] > > ______________________________________________ > 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.
