Erin, ?merge
Try c.df=merge(a.df,b.df,by.x="PATIENT_ID",by.y="ID") hope it helps Weidong ______________________________________________ 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.
