Hi Farnoosh, Try: library(plyr)
res <- join(`DATA-A`,`DATA-B`,by="Var1",type="right")[,c(3,1:2,4)] head(res) # ID Var1 Var2 var3 #1 1 AETNA CARDINAL CARE TIER 2 <NA> 10 #2 2 AETNA EPO Group1 110 #3 3 BLUE CARD INTE Group1 2 #4 4 BLUE CROSS AUTO Group1 25 #5 5 BLUE CROSS CA Group1 33 #6 6 LOCKHEED Group2 40 A.K. On Wednesday, February 19, 2014 6:03 PM, farnoosh sheikhi <farnoosh...@yahoo.com> wrote: Hi Arun, I have two data files, DataA looks like below. I need to add Var2 to DataB (2nd data set), but not sure if I can just merge based on Var1. Thanks for your help. DATA-A: Var1 Var2 AETNA AF Group1 AETNA BAY Group1 AETNA BMT Group1 AETNA BR Group1 AETNA CARE Group1 AETNA TIER 2 Group1 AETNA EPO Group1 BLUE CARD INTE Group1 BLUE CROSS AUTO Group1 BLUE CROSS CA Group1 LOCKHEED Group2 OPEN PLAN Group2 MED GRP Group2 MED FOUNDATION Group2 AETNA PMG OF SAN JOSE Group2 DATA-B: ID Var1 var3 1 AETNA CARDINAL CARE TIER 2 10 2 AETNA EPO 110 3 BLUE CARD INTE 2 4 BLUE CROSS AUTO 25 5 BLUE CROSS CA 33 6 LOCKHEED 40 7 OPEN PLAN 55 8 MED GRP 1 9 MED FOUNDATION 1 10 AETNA PMG OF SAN JOSE 0 11 AETNA AF 22 12 AETNA BAY 333 13 AETNA BMT 22 14 AETNA BR 22 15 BLUE CARD INTE 11 16 BLUE CARD INTE 10 Regards, Farnoosh Sheikhi ______________________________________________ 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.