The MDCDATA statement prepares data for use by PROC MDC when the choice-specific information is stored in multiple variables
(for example, see Figure 25.1 in the section Conditional Logit: Estimation and Prediction).
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VARLIST (name1 = (var1 var2 …) name2 = (var1 var2 …) …)
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creates name variables from a multiple-variable list of choice alternatives in parentheses. The choice-specific dummy variables are created
for the first set of multiple variables. At least one set of multiple variables must be specified. The order of (var1 var2 ...) in the VARLIST option determines the numbering of the alternative; that is, var1 corresponds to alternative 1, var2 corresponds to alternative 2, and so on.
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SELECT=(variable)
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specifies a variable that contains choices for each individual. The SELECT= variable needs to be a character-type variable, with values that match variable names in the first VARLIST option: name1=(var1 var2 ...).
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ID=(name)
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creates a variable that identifies each individual.
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ALT=(name)
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identifies selection alternatives for each individual.
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DECVAR=(name)
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creates a 0/1 variable that indicates the choice made for each individual.
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OUT=SAS-data-set
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specifies a SAS data set to which modified data are output.