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.varConstPower(const, power, form, fixed)form. If either argume~ v, or
~ v | g, specifying a variance covariate v and,
optionally, a grouping factor g for the coefficients. The
variance covariate must evaluate toconst and/or
power, consisting of numeric vectors, or lists of numeric
values, specifying the values at which some or all of the
coefficients in the variance function should be fixed. varConstPower object representing a constant plus power
variance function structure, also inheriting from class
varFunc.varWeights.varFunc, coef.varConstPowervf1 <- varConstPower(1.2, 0.2, form = ~age|Sex)Run the code above in your browser using DataLab