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Re: st: One to N matching


From   "Austin Nichols" <austinnichols@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: One to N matching
Date   Tue, 18 Nov 2008 11:32:19 -0500

Gao Liu--
Actually, I think you are looking for -psmatch2- (findit psmatch2).
Or did you want to program the matching by hand?  That is also
possible, and not very hard in the case where all you want is the
nearest N matches.  However, note that the order of matching will
matter in the situation you describe--matching without replacement--so
you should probably do the matching many times and compute statistics
using the rules of variance computation for multiple imputation.

On Tue, Nov 18, 2008 at 11:07 AM, Richard Goldstein
<richgold@ix.netcom.com> wrote:
> for already existing programs, rather than writing your own, I would start
> with -vmatch- (user-written, type -findit vmatch-)
>
> I'm not sure it will cover your last criterion (used only once) but if not
> it should be easy to eliminate those
>
> Rich
>
> Gao Liu wrote:
>>
>> Dear Statlist:
>>
>> I have a question about one to N matching.
>>
>> I have a dataset containing three variables: id, score, case, where
>> case is a dummy variable indicating whether or not the observation is
>> in the case group. How can I match each case observation to N non-case
>> observation based on the score?  Each case observation matches to the
>> N non-case observations with the closest scores, but no case
>> observation can match the same observation (i.e. the non-case
>> observation can be used only one time).
>>
>> Thank you
>>
>> Best
>>
>> Gao
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