If the
formula(object) includes a
. term, representing
a fitted object, the variance covariate needs to be updated upon
completion of an optimization cycle (in which the variance function
weights are kept fixed). This method function allows a reevaluation of
the variance covariate using the current fitted object and,
optionally, other variables in the original data.
USAGE:
update(object, data)
REQUIRED ARGUMENTS:
object
an object inheriting from class
varFunc,
representing a variance function structure.
data
a list with a component named
"." with the current
version of the fitted object (from which fitted values, coefficients,
and residuals can be extracted) and, if necessary, other variables
used to evaluate the variance covariate(s).
VALUE:
if
formula(object) includes a
"." term, an
varFunc
object similar to
object, but with the
variance covariate reevaluated at the current fitted object value;
else
object is returned unchanged.