a formula object, describing the model whose alias pattern is to be
studied.
OPTIONAL ARGUMENTS:
data
data frame in which the model is to be studied.
Arguments for function
can also be supplied to this function.
VALUE:
the alias pattern found by fitting the model (with
aov).
DETAILS:
This function is a method for the generic function
for class formula.
It can be invoked by calling
for an object x of the appropriate class, or directly by calling
regardless of the class of the object.