varConstPower: Constant Plus Power Variance Function
Description
This function is a constructor for the varConstPower class,
representing a constant plus power variance function
structure. Letting $v$ denote the variance covariate and
$\sigma^2(v)$ denote the variance function evaluated at
$v$, the constant plus power variance function is defined as
$\sigma^2(v) = (\theta_1 + |v|^\theta_2)^2$, where $\theta_1,\theta_2$ are the variance
function coefficients. When a grouping factor is present, different
$\theta_1,\theta_2$ are used for each factor level.
Usage
varConstPower(const, power, form, fixed)
Arguments
Value
a varConstPower object representing a constant plus power
variance function structure, also inheriting from class
varFunc.
References
Pinheiro, J.C., and Bates, D.M. (2000) "Mixed-Effects Models
in S and S-PLUS", Springer.