Find Terms Common to Two Formulas

DESCRIPTION:

A utility to help detemine whether a new formula has terms implied by an old formula.

USAGE:

match.formula(F1, F2) 

REQUIRED ARGUMENTS:

F1
a formula object (the old formula)
F2
a formula object (the new formula)

VALUE:

returns a logical vector named by the labels of the terms in F1. A value of NA is returned if there are terms or variables in F2 that do not appear in F1. The returned value has a attribute order that indicates the order of occurence in F1 of the common terms.

DETAILS:

This is a utility for update.fac.aov.

SEE ALSO:

, .

EXAMPLES:

match.formula(~ pH*thimer*gent,~ thimer + pH + pH:thimer) 
match.formula(~ thimer + pH,~ pH*thimer) 
match.formula(rate ~ thimer * pH,sqrt(rate) ~ pH*thimer)