Thanks very much! Gurpal Centrica Energy.
On Wed, Oct 28, 2009 at 4:31 PM, William Dunlap <wdun...@tibco.com> wrote: > > -----Original Message----- > > From: r-help-boun...@r-project.org > > [mailto:r-help-boun...@r-project.org] On Behalf Of Erik Iverson > > Sent: Wednesday, October 28, 2009 9:22 AM > > To: Gurpal Kalsi; r-help@r-project.org > > Subject: Re: [R] Selecting rows according to a column > > > > Hello, > > > > Here's an idea: > > > > ifelse(z$c == "a", z$a, z$b) > > If there may be many columns to select from (so > the nested ifelse's become tedious) one might try > > z[,-3][cbind(seq_len(nrow(z)),z$c)] > [1] 1 2 30 40 50 > The initial [,-3] is there only so when the data.frame > is converted to a matrix by [.data.frame's processing > of a matrix subscript it becomes a numeric matrix, not > a character matrix. > > Bill Dunlap > Spotfire, TIBCO Software > wdunlap tibco.com > > > > > > > > -----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. > > > [[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.
