From:Kosuke Imai &lt;kimai(a)princeton.edu&gt;  To: Ana Kolar &lt;annakolar(a)yahoo.com&gt; Cc: &quot;matchit(a)lists.gking.harvard.edu&quot; &lt;matchit(a)lists.gking.harvard.edu&gt;  Sent: Monday, 17 September 2012, 2:19  Subject: Re: [matchit] Matching with true propensity score     Hi Ana,  You can use your own distance matrix (including the true propensity score in a simulation study) in MatchIt: http://gking.harvard.edu/node/4355/rbuild_documentation/How_Do_I3.html Best, Kosuke Department of Politics Princeton University http://imai.princeton.edu <http://imai.princeton.edu/> On Sep 16, 2012, at 3:51 PM, Ana Kolar wrote:       

     From:"Stuart, Elizabeth A." &lt;estuart(a)jhsph.edu&gt;  To: Ana Kolar &lt;annakolar(a)yahoo.com&gt;om>; Kosuke Imai &lt;kimai(a)Princeton.Edu&gt; Cc: MatchIt &lt;matchit(a)lists.gking.harvard.edu&gt;  Sent: Tuesday, 18 September 2012, 16:32  Subject: Re: [matchit] Matching with true propensity score     Re: [matchit] Matching with true propensity score Hi Ana, I have sent MatchIt my own propensity score using code like: m.out.gbm.att <- matchit(treat ~ age + educ + black + hispan + married + re74 + re75, data=lalonde, distance=lalonde$pscore) (Where in this case “pscore” in the lalonde dataset is the propensity score values I had estimated myself).  Note that it is the distance option, not the distance.options option...   And yes, you have to specify the formula still, so matchit know what variables on which to calculate balance, but it doesn’t actually estimate the propensity score using that formula; it uses the propensity scores you send it in the distance option.   One minor note is that in your email below you mention a “distance matrix” but really matchit will just take a distance vector (one propensity score for each person).  If you have a distance matrix you may want to look at using some of Ben Hansen’s optmatch functions, which take a distance matrix.   Liz On 9/18/12 10:11 AM, "Ana Kolar" &lt;annakolar(a)yahoo.com&gt; wrote: Hi Kosuke, > >If I understand this correctly, by using my own distance matrix (ps.true) the function should look something like that: >m.out.base <- matchit(formula, data, method, distance.options = list(ps.true)) > >So, I have to specify the formula for estimating PS although I'm using then the true PS for matching which I specify in the distance.options=list(ps.true)? Does this mean that when I specify distance.option argument, the program doesn't estimate PS although the formula for it has to be provided? > >The thing is that I've tried two ways: >(i) distance.options=ps.true (where ps.true object is already a list >(ii) distance.options=list(ps.true) (where ps.true object is a vector) > >In none of these trials things worked out so I'm wondering where I might get it wrong. Your help will be greatly appreciated! > >Best wishes, > >Ana > > > >  >>  >> >>  >>>>>>  From:Kosuke Imai &lt;kimai(a)princeton.edu&gt; >> To: Ana Kolar &lt;annakolar(a)yahoo.com&gt; >>Cc: &quot;matchit(a)lists.gking.harvard.edu&quot; &lt;matchit(a)lists.gking.harvard.edu&gt; >> Sent: Monday, 17 September 2012, 2:19 >> Subject: Re: [matchit] Matching with true propensity score >>  >>  >>Hi Ana, >> >> You can use your own distance matrix (including the true propensity score in a simulation study) in MatchIt: http://gking.harvard.edu/node/4355/rbuild_documentation/How_Do_I3.html >> >>Best, >>Kosuke >> >>Department of Politics >>Princeton University >>http://imai.princeton.edu <http://imai.princeton.edu/>  <http://imai.princeton.edu/> >> >>On Sep 16, 2012, at 3:51 PM, Ana Kolar wrote: >> >>> Hi there, >>> >>> I'm wondering if Matchit package allows to match on the true propensity score - meaning that instead of estimating PS (what matchit function does) I would be able to provide a vector of true propensity scores which would be then used in the process of matching. The second thing that I'm interested in is, whether it is possible to do Mahalanobis distance matching and not only propensity score matching. I did check your documentation (perhaps not carefully enough) but couldn't find my answers there. >>> >>> I'm looking forward to hearing from you soon! >>> >>> Ana >>> - >>> --- >>> MatchIt mailing list served by HUIT >>> List Address: matchit(a)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(a)lists.gking.harvard.edu >>> https://lists.gking.harvard.edu/mailman/listinfo/matchit >> >> >> >>  >> >>  >>   > >