On Thu, Apr 23, 2009 at 5:11 PM, ozan bakis <ozanba...@gmail.com> wrote: > Dear R Users, > I have the following data frame: > > v1 <- c(rep(10,3),rep(11,2)) > v2 <- sample(5:10, 5, replace = T) > v3 <- c(0,1,2,0,2) > df <- data.frame(v1,v2,v3) >> df > v1 v2 v3 > 1 10 9 0 > 2 10 5 1 > 3 10 6 2 > 4 11 7 0 > 5 11 5 2 > > I want to add a new column v4 such that its values are equal to the value > of v2 conditional on v3=0 for each subgroup of v1. In the above example, > the final result should be like > > df$v4 <- c(9,9,9,7,7) >> df > v1 v2 v3 v4 > 1 10 9 0 9 > 2 10 5 1 9 > 3 10 6 2 9 > 4 11 7 0 7 > 5 11 5 2 7 > > > I tried the following commands without success. > > df$v4 <- ave(df$v2, df$v1, FUN=function(x) x[df$v3==0]) > tapply(df$v2, df$v1, FUN=function(x) x[df$v3==0]) > by(df$v2, df$v1, FUN=function(x) x[df$v3==0]) > > Any help? Thanks in advance!
Here's one approach with the plyr package, http://had.co.nz/plyr library(plyr) ddply(df, .(v1), transform, v4 = v2[v3 == 0]) Hadley -- http://had.co.nz/ ______________________________________________ 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.