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To Work with setx()

In the case of setx(), most models will use setx.default(), which in turn relies on the generic R function model.matrix(). For this procedure to work, your list of output must include:

• terms, created by model.frame(), or manually;
• formula, the formula object input by the user;
• xlevels, which define the strata in the explanatory variables; and
• contrasts, an optional element which defines the type of factor variables used in the explanatory variables. See help(contrasts) for more information.

If your model output does not work with setx.default(), you must write your own setx.contrib() function. For example, models fit to multiply-imputed data sets have output from zelig() of class "MI". The special setx.MI() wrapper pre-processes the zelig() output object and passes the appropriate arguments to setx.default().