update.varFunc             package:nlme             R Documentation

Update varFunc Object

Description:

     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:

     ## S3 method for class 'varFunc':
     update(object, data, ...)

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).

     ...: some methods for this generic require additional arguments. 
          None are used in this method.

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.

Author(s):

     Jose Pinheiro Jose.Pinheiro@pharma.novartis.com and Douglas Bates
     bates@stat.wisc.edu

See Also:

     'needUpdate', 'covariate<-.varFunc'

