Dear R, I've got a data frame with children examined multiple times and at various ages. I'm trying to find the first age at which another variable (LDL-Cholesterol) is >= 130 mg/dL; for some children, this may never happen. I can do this with transformBy and ddply, but with 10,000 different children, these functions take some time on my PCs - is there a faster way to do this in R? My code on a small dataset follows.
Thanks very much, David Freedman d<-data.frame(id=c(rep(1,3),rep(2,2),3),age=c(5,10,15,4,7,12),ldlc=c(132,120,125,105,142,160)) d$high.ldlc<-ifelse(d$ldlc>=130,1,0) d library(plyr) d2<-ddply(d,~id,transform,plyr.minage=min(age[high.ldlc==1])); library(doBy) d2<-transformBy(~id,da=d2,doby.minage=min(age[high.ldlc==1])); d2 -- View this message in context: http://www.nabble.com/long-format---find-age-when-another-variable-is-first-%27high%27-tp23706393p23706393.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.
