| varFixed {nlme} | R Documentation |
Fixed Variance Function
Description
This function is a constructor for the varFixed class,
representing a variance function with fixed variances. Letting v
denote the variance covariate defined in value, the variance
function \sigma^2(v) for this class is
\sigma^2(v)=|v|. The variance covariate v is
evaluated once at initialization and remains fixed thereafter. No
coefficients are required to represent this variance function.
Usage
varFixed(value)
Arguments
value |
a one-sided formula of the form |
Value
a varFixed object representing a fixed variance function
structure, also inheriting from class varFunc.
Author(s)
José Pinheiro and Douglas Bates bates@stat.wisc.edu
References
Pinheiro, J.C., and Bates, D.M. (2000) "Mixed-Effects Models in S and S-PLUS", Springer.
See Also
varClasses,
varWeights.varFunc,
varFunc
Examples
vf1 <- varFixed(~age)