Hello, I am trying to re-code all my programs from SAS into R.
In SAS I use the following code: proc sort data=upper; by tdate stock_symbol expire strike; run; data upper1; set upper; by tdate stock_symbol expire strike; if first.expire then output; rename strike=astrike; run; on the following data set: tdate stock_symbol expiration strike 9/11/2012 C 9/16/2012 11 9/11/2012 C 9/16/2012 12 9/11/2012 C 9/16/2012 13 9/12/2012 C 9/16/2012 14 9/12/2012 C 9/16/2012 15 9/12/2012 C 9/16/2012 16 9/12/2012 C 9/16/2012 17 to get the following results: tdate stock_symbol expiration strike 9/11/2012 C 9/16/2012 11 9/12/2012 C 9/16/2012 14 How would I replicate this kind of logic in R? I have seen PLY & data.table packages mentioned but don't see how they would do the job. Thanks ahead for your help -- View this message in context: http://r.789695.n4.nabble.com/How-to-replicate-SAS-by-group-processing-in-R-tp4645753.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.
