| varFunc {nlme} | R Documentation | 
If object is a one-sided formula, it is used as the argument to
varFixed and the resulting object is returned. Else, if
object inherits from class varFunc, it is returned
unchanged. 
varFunc(object)
object | 
 either an one-sided formula specifying a variance
covariate, or an object inheriting from class   | 
an object from class varFunc, representing a variance function
structure. 
Jose Pinheiro and Douglas Bates bates@stat.wisc.edu
summary.varFunc,
varFixed,
varWeights.varFunc,
coef.varFunc
vf1 <- varFunc(~age)