I want to find the last record for each person_id in a data frame (from a SQL database) ordered by date. Is there a better way than this for loop?
for (i in 2:length(history[,1])) { if (history[i, "person_id"] == history[i - 1, "person_id"]) history[i, "order"] = history[i - 1, "order"] + 1 # same person else history[i, "order"] = 1 # new person } # ignore all records except the last for each con_id history2 <- subset(history, order == 1) Andrew ______________________________________________ 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.