Hi Karen,
Yes, I believe that is correct. The Mahalanobis distance is only defined relatively, for
pairs of 2 subjects (i.e., the distance between A and B is different from the distance
between A and C). It is not like propensity score matching, where each person has a
particular value and then we match on that-with Mahalanobis matching person "A"
doesn't have their own value; the matches are defined only by calculating their
distance with the other individuals in the data. So there isn't really a simple
"distance" variable/measure on which you could look at the diagnostics.
I hope this helps.
Liz
On 1/24/11 9:10 AM, "Karen Johnson" <karenjohnson(a)prodigy.net> wrote:
Hello,
I'm very new to R and to MatchIt, so I'm not really sure what I should be
seeing...but when I run it using a Mahalanobis distance, all the distance values in the
resulting output are "NA". This happens both with my "real" data and
with the LALONDE data. Is this correct? (Note: I'm running the latest versions of
R and MatchIt).
Thanks.
--Karen
--
MatchIt mailing list served by Harvard-MIT Data Center
List Address: matchit(a)lists.gking.harvard.edu
Subscribe/Unsubscribe:
http://lists.gking.harvard.edu/?info=matchit
MatchIt Software and Documentation:
http://gking.harvard.edu/matchit/
Browse/Search List Archive:
http://lists.hmdc.harvard.edu/lists/matchit/