[R] GenMatch providing different results

[Rob Wood]

Hi there,

I'm performing some propensity score matching in R, where I am using
GenMatch() to generate a weight matrix for the covariates, before plugging
that into Match(). However, I keep on getting different results each time I
run the code. I'm using int.seed and unif.seed in GenMatch, but to no avail.
I've also noticed that when I just use Match() without previously using
GenMatch(), the results are consistent each time, which is why I believe
GenMatch() is causing the problem:

A slight extract of my code looks like this:

######Genetic Matching
gmatch <- GenMatch(Tr=treatment, X=X, estimand="ATT", M=1, pop.size=50,
max.generations=15, wait.generations=5, caliper=0.05, ties=FALSE,
int.seed=240690, unif.seed=021189)
  
###Actual matching
 match <- Match(Y=outcome, Tr=treatment, X=X, estimand="ATT",
Weight.matrix=gmatch)

summary(match)

Can anyone point me in the right direction to diagnose my problem?

Thanks,

Rob.
  



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