Steve, Your example seems to work quite well, except I get a summary printout showing all the true and false values.
> !duplicated(ladata2$Vin) [1] TRUE TRUE TRUE TRUE What I would like to do is have the true/false values appended to a column at the end of my dataset so that when done, I can selectively either keep or drop rows based on whether they are true or false. I have tried to get this done with several variable creation statements with no luck. Any ideas on how I can modify your code to get the following: Plate, Date, True.False Plate1, 013110, true Plate 1, 010110, false Plate 1, 010109, false Plate 2, 020110, true To everyone else, thanks greatly for your examples! I have learned from each of your suggestions. -- View this message in context: http://n4.nabble.com/First-Last-Data-row-selection-tp1566260p1566801.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.