Hi,
For optimal matching, my guess is that you do not have enough
observations to do a higher ratio matching. Some of the constraints
must have been violated.
For genetic matching, we do not keep ties in matchit when doing the
ratio matching. This might be a causing error. So, you might want to
explicitly tell matchit() not to keep ties.
Kosuke
On Dec 4, 2009, at 12:29 AM, Sinan Gemici wrote:
Dear All,
I'm running matches on the same sample using nearest-neighbor,
optimal, and genetic matching.
With NN matching I use a 5-to-1 ratio and it works just fine.
With OPTIMAL matching, a 2-to-1 ratio works fine but any higher
ratio produces the following error message:
"Error in fullmatch(d, min.controls = ratio, max.controls = ratio,
omit.fraction = (n0 - : negative 'omit.fraction' with
'min.controls' >= 2 not permitted"
With GENETIC matching, a 2-to-1 ratio works fine but any higher
ratio produces the following error message:
"Error: subscript out of bounds"
Am I making a mistake or is 2-to-1 the highest possible ratio in
MatchIt for optimal and genetic matching?
Thank you much,
Sinan
--
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/
--
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/