We'll need to do it on Monday. I don't like to give special exams
before the main exam.
Tony
Peter A. Lachenbruch
Department of Public Health
Oregon State University
Corvallis, OR 97330
Phone: 541-737-3832
FAX: 541-737-4001
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of David Kantor
Sent: Thursday, April 03, 2008 8:53 AM
To: Statalist
Subject: st: mahapick updates
Thanks to Kit Baum, updates to the mahapick package are now available on
SSC.
The mahapick package has programs to calculate a distance measure
(propensity score, dissimilarity measure) between observations, and
to choose a set of close matches for a selected subset of observations.
There are two important changes:
1, this now implements a true Mahalanobis distance measure -- whereas
previously, it was the normalized Euclidean distance. The true
Mahalanobis measure accounts for correlation between variables. (The
old behavior is available as an option.)
2, the new program mahascores enables you to directly obtain the
distance measures between all pairs of observations. The concept of
"treated" observations is optional. And, while there is some overlap
with some of the functionality of mahapick, this would be the
preferred method if all you want is the distance measure (and don't
need, at this stage, to select the closest matches). The results can
be placed into the current dataset, a separate dataset, or a matrix.
There are other enhancements that should give users more control.
Thanks also go to Heiko Giebler of Wissenschaftszentrum Berlin fur
Sozialforschung gGmbH -- for the suggestions and advice that led to
these improvements.
To download...
ssc desc mahapick
ssc inst mahapick
If any users try it and have any problems, comments, or suggestions,
I'd like to hear them.
Best wishes,
--David Kantor
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