CEM objects have a value strata which returns the vector of the stratum
number in which each observation belongs. This can be used to fairly easily
reconstruct the matched data. I don't know of any a more straightforward
way, but that should work.
As for the warnings- I don't know what the issue is. I tried it over here
and I get the same problem, which appears to be contingent on specifying
k2k=TRUE. Error notwithstanding the procedure seems to work just fine (it
does produce a 1:1 match and a full object), but I understand why you'd be
concerned. I'll leave the answer to better informed people...
Brandon
On Mon, Apr 27, 2009 at 7:08 PM, Schmidt, William <wschmidt at hbs.edu> wrote:
If anyone is comfortable with CEM, I have a couple of
questions:
1. After running CEM, how do I access the matched data for further
analysis? Using MatchIt, match.data calls the data. What is the equivalent
in cem?
2. I am trying to refine my CEM by using k2k matching. I have tried
this two ways:
Option 1:
CEMMatch <- cem(treatment="Treated", data=Test, drop=dropvar,
cutpoints=MyCuts, k2k=TRUE)
Option 2:
CEMMatch <- cem(treatment="Treated", data=Test, drop=dropvar,
cutpoints=MyCuts)
CEMMatch1 <- k2k(CEMMatch, Test, "euclidean", 1)
In both options, I am getting the results below. We get the same set of
warnings when we replicate the example in the R help file for cem. Do these
warnings mean anything that needs to be addressed?
There were 50 or more warnings (use warnings() to see the first 50)
warnings()
Warning messages:
1: In min(x, na.rm = TRUE) : no non-missing arguments to min; returning Inf
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