In the STAGEIN= data set, missing values are allowed only for the STAGE= and TYPE= variables when the information of a stage is specified in more than one observation. In this case, missing values for the STAGE= and TYPE= variables are not allowed for the first observation defining the stage. Missing values for the OUTCOME=, GIVEN=, EVENT=, STATE=, and ACTION= variables are ignored. Missing values for the REWARD=, PROB=, and VALUE= variables are treated as . Missing values for the SUCCESSOR= variables are ignored if the value for the corresponding OUTCOME= variable is also missing.