Hi, I'm fairly new to R but I have a large dataset (300000 obs) containing patient material. Some patients came 2-9 times during the three year observation period. The patients are identified by a unique idnr, the sessions can be distinguished using the session date. How can I recode the date of the session to a session id (1-9). This would be necessary to obtain information and do some analysis on the first occurence of a specific patient or to look for trends.
Thanks JP Bogers University of Antwerp [[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.