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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 14:37:52 -0500

Nick--
I don't think -duplicates- addresses the issue.  The idea is, for
observation 1, find the k obs with the closest value of p (k a scalar,
say 4, and p a variable, measuring for example a propensity).  Then
repeat for observation 2, but do not pick any of the obs you picked
for observation 1.  Et cetera. "Duplicates" in this setting means
picking observations more than once, I believe.

This is presumably needed for some nonstandard form of propensity
score matching--on which see Rosenbaum and Rubin (1983), linked
directly from p.26 of http://pped.org/stata/ciwod.pdf

On Tue, Nov 18, 2008 at 2:17 PM, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> At least part of this sounds very easy. If duplicates are not allowed,
> remove them first with -duplicates-.
>
> Nick
> n.j.cox@durham.ac.uk
>
> Gao Liu
>
> vmatch can match all observations based on certain criteria, like
> within some distance. However, what I want is the nearest N
> observations, where n is a fixed number. Also, duplicates are not
> allowed.
>
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