Hi Hong Ooi, Thanks for your reply! I tried this option as well, but the result is not as I expect:
> y$x4 <- ifelse(y$x1>0,y$x2,y$x3) > y $x4 logical(0) > class(y) [1] "list" Any more ideas? Thanks, Sander. Hong Ooi wrote: > _______________________________________________________________________________________ > > Note: This e-mail is subject to the disclaimer contained at the bottom of > this message. > _______________________________________________________________________________________ > > > x2 and x3 are not separate objects, but columns of y. So you need to specify > that. > > y$x4 <- ifelse(y$x1 > 0, y$x2, y$x3) > > > > ________________________________ > > From: [EMAIL PROTECTED] on behalf of Sander Oom > Sent: Sat 11/03/2006 11:23 PM > To: r-help@stat.math.ethz.ch > Subject: [R] Conditional operation on columns in data frame > > > > Dear R-users, > > I need to do an SQL like, conditional, operation on a data frame using > an ifelse construction. However I can not get it to work. > > Example: >> x1 <- rnorm(10) >> x2 <- rnorm(10) >> x3 <- rnorm(10) >> x3 <- NA >> y <- cbind(x1,x2,x3) >> y > x1 x2 x3 > [1,] -0.56927780 -0.30952274 NA > [2,] 0.16355087 0.05911772 NA > [3,] -0.21899354 2.04583752 NA > [4,] 0.06368076 1.11661608 NA > [5,] -1.30249878 -0.63354373 NA > [6,] 0.04842365 1.47591928 NA > [7,] -0.32364275 -0.62201121 NA > [8,] -0.70427823 -0.15485223 NA > [9,] -0.39563916 2.23504977 NA > [10,] -1.24102239 -0.40991140 NA > > Now I want to fill a new column with values from either x2 or x3, > depending on the value in x1. I thought of something like this: > y$x4 <- ifelse(y$x1>0,x2,x3) > y$x4 <- apply(y,1, function(x) {ifelse(x$x1>0,x$x2,x$x3) }) > > But obviously this did not give the right result. > > Any suggestions? > > Thanks in advance, > > Sander. > > ______________________________________________ > R-help@stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html > > > > > _______________________________________________________________________________________ > > The information transmitted in this message and its attach...{{dropped}} ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html