Hi: Here are a few ways:
(1) ave(): transform(dat, dropout.time = ave(y, id, FUN = function(x) sum(!is.na(x)))) (2) same as (1) without the transform() statement: dat$dropout.time <- ave(y, id, FUN = function(x) sum(!is.na(x))) dat (3) ddply() in the plyr package: library(plyr) snisna <- function(x) sum(!is.na(x)) ddply(dat, .(id), transform, dropout.time = snisna(y)) HTH, Dennis On Sun, May 30, 2010 at 7:25 PM, john james <dnt...@yahoo.com> wrote: > Dear R users, > > Please assist me with the following problem. I have a dataset that looks > like the following: > > dat<-data.frame( > 'id'=rep(c(1,2,3),each=3), > 'time'=rep(c(1,2,3),3), > 'y'= c(2,2,NA,2,NA,NA,2,5,7) > ) > > > I wish to create a variable for dropout time in dataframe 'dat' such that > the dropout time is the time to drop out by the subject as follows: > > > dat<-data.frame( > 'id'=rep(c(1,2,3),each=3), > 'time'=rep(c(1,2,3),3), > 'y'= c(2,2,NA,2,NA,NA,2,5,7), > 'dropout time'=c(2,2,2,1,1,1,3,3,3) > ) > > Any help will be appreciated. Many thanks in advance. > > james > > > > [[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. > > [[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.
