% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/start_values.R
\name{.get_phi_start}
\alias{.get_phi_start}
\title{Internal Helper to Calculate Initial Phi}
\usage{
.get_phi_start(fit, n_eff, linkinv, mu.eta)
}
\arguments{
\item{fit}{An 'lm.fit' object.}

\item{n_eff}{The effective number of observations used in the fit.}

\item{linkinv}{The inverse link function.}

\item{mu.eta}{The derivative of the mean w.r.t. eta (d(mu)/d(eta)).}
}
\value{
A single numeric value for phi_start.
}
\description{
Calculates the initial value for the precision parameter phi based on the
residuals of an initial 'lm.fit' object. The formula is adapted and
empirically improved from Ferrari & Cribari-Neto (2004) — specifically,
the "-1" term in the original precision estimator is omitted, as Monte
Carlo simulations showed better optimization performance without it.
}
\keyword{internal}
