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...fic terminology. I would appreciate it if you could take a moment to enlighten me. Thanks, Bob mydata <- data.frame( id = c('001','001','001','002','003','003'), math = c(80,75,70,65,65,70), reading = c(65,70,88,NA,90,NA) ) mydata mylast <- lapply( split(mydata,mydata$id), tail, n=1) mylast class(mylast) #It's a list, so lapply will so *something* with it. #This gets the desired result: do.call("rbind", mylast) #This doesn't do the same thing, which confuses me: lapply(mylast,rbind) #...and data.frame won...