Using Genmod, I am estimating a zero-inflated Poisson model. I want to test a contrast involving covariates that appear only in the Zeromodel statement. There should be no problem doing so since this example appears in the SAS 9.4 documentation: proc Genmod; class a b; model y=a / dist=zip; zeromodel b; contrast 'Label2' A 1 -1 @Zero B 1 -1; As you can see, there is no overlap in this model between the covariates in the Model statement and those in the Zeromodel statement, and the requested Contrast involves covariates in both those statements. But when I try to do something exactly like the example code above, I get this error message: "ERROR: Effects used in the CONTRAST statement must have appeared previously in the MODEL statement." Any suggestions would be appreciated. I am baffled.
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