Construct a design row in the fitted coding. When marginal=true, unspecified factors
are averaged equally and covariates fixed at their complete-case means. The expectation
is evaluated algebraically by variable; no exponentially large reference grid is built.
Construct a design row in the fitted coding. When marginal=true, unspecified factors are averaged equally and covariates fixed at their complete-case means. The expectation is evaluated algebraically by variable; no exponentially large reference grid is built.