Error: A feasible optimal fixed ratio matching that has the specified parameters does not exist. I am trying to do propensity score matching using method = optimal and caliper=0.25, however, I keep getting an error saying "A feasible optimal fixed ratio matching that has the specified parameters does not exist". When I change use caliper=., it works fine. I had an understanding that if caliper value is unspecified, the default caliper of 0.25 is used. However, providing value of 0.25 in caliper explicitly gives me an error. Can I still say that Caliper=. means that the caliper value considered while matching is the default value of 0.25?
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