Model Updating

Usage

update.formula(old, new)

Arguments

old a model formula to be updated.
new a formula giving a template which specifies how to update.

Description

update.formula is used to update model formulae. This typically involves adding or dropping terms, but updates can be more general.

The function works by first identifying the left-hand side and right-hand side of the old formula. It then examines the new formula and substitutes the lhs of the old formula for any occurence of "." on the left of new, and substitutes the rhs of the old formula for any occurence of "." on the right of new.

The updated formula is returned.

See Also

terms, model.matrix.


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