These tell you the first and last row for each plate: !duplicated(df$plate) !duplicated(df$plate, fromLast=TRUE) Hope that helps. Steve
>>> From: wookie1976 <joe.roesc...@revecorp.com> To:<r-help@r-project.org> Date: 24/Feb/2010 6:54 a.m. Subject: [R] First. Last. Data row selection I am in the process of switching from SAS over to R. I am working on very large CSV datasets that contain vehicle information. As I am processing the data, I need to select the first (or sometimes the second) record (by date) for any records that have the same license plate number. In SAS, there is a function called 'first.' that can be used on sorted datasets to pull out those first entries for each occurrence of a particular variable (in this case the variable is 'license plate') found in the data. I have spent some time looking around and cannot seem to find an equivalent function in R. Can anyone recommend an efficient technique that would pull this off? I assume the database must first be sorted by vehicle plate and date, and then apply the filter or function. Any help would be greatly appreciated. Thanks, Joe -- View this message in context: http://n4.nabble.com/First-Last-Data-row-selection-tp1566260p1566260.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 ( http://www.r/ )-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]] ______________________________________________ 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.
