Thank you liz. This helps greatly. George Sent on the fly George E. Higgins, Ph.d. On Aug 5, 2013, at 8:16 PM, "Stuart, Elizabeth A." <estuart@jhsph.edu<mailto:estuart@jhsph.edu>> wrote: Hi George, Yes, that is very easy. See this FAQ: http://r.iq.harvard.edu/docs/matchit/2.4-20/How_Do_I3.html Basically you use a command like: m.out.fr1 <- matchit(treat ~ var1 + var2 + var3, data=dta, distance=dta$pscore) The formula given at the beginning of the command is just to tell MatchIt the variables on which to calculate balance; it uses the propensity scores in the dta$pscore vector for the matching. Thanks, Liz On Aug 5, 2013, at 7:58 AM, "Higgins,George Edward" <george.higgins@louisville.edu<mailto:george.higgins@louisville.edu>> wrote: Hello, I hope that this finds you well. I have a data set where I have estimated the propensity score previously, and now I need MatchIt to read that propensity score and perform the matching process. With this in mind, I was wondering if there was syntax or code that could be used to have MatchIt use this existing propensity score? Thank you. George George E. Higgins, Ph.D. Professor Editor of Journal of Criminal Justice Education 2301 South Third Street 208 Brigman Hall Department of Justice Administration University of Louisville Louisville, KY 40292 Phone: (502) 852-0331 Fax: (502) 852-0065 - --- MatchIt mailing list served by HUIT List Address: matchit@lists.gking.harvard.edu<mailto:matchit@lists.gking.harvard.edu> Subscribe/Unsubscribe: http://lists.gking.harvard.edu/mailman/listinfo/ei MatchIt Software and Documentation: http://gking.harvard.edu/matchit/ Browse/Search List Archive: http://lists.gking.harvard.edu/mailman/private/matchit/ Matchit mailing list Matchit@lists.gking.harvard.edu<mailto:Matchit@lists.gking.harvard.edu> To unsubscribe from this list or get other information: https://lists.gking.harvard.edu/mailman/listinfo/matchit