Thank you Michael, that worked perfectly! Now I wonder, if it is possible to break my data further apart and put it together again. Assume I include a column for an ID in the data frame like this:
dattrial2<-data.frame(a=c(1,NA,NA,NA,2,3), Week=c(3,3,3,4,4,4), AnimalID=c("Ernie","Bert", "Ernie", "Bert", "Bert", "Ernie")) Is it possible to get two different lists in the output, one for Ernie and one for Bert? Or do I have to do it seperately for each animal? Thank you again! I learn a lot by doing and by people helping me. Thank you for the hint with the paper. -- View this message in context: http://r.789695.n4.nabble.com/count-NAs-per-week-tp4643351p4643371.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.