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 varFixed object representing a fixed 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.