\HeaderA{vcov}{Calculate Variance-Covariance Matrix for a Fitted Model Object}{vcov}
\methaliasA{vcov.glm}{vcov}{vcov.glm}
\methaliasA{vcov.gls}{vcov}{vcov.gls}
\methaliasA{vcov.lm}{vcov}{vcov.lm}
\methaliasA{vcov.lme}{vcov}{vcov.lme}
\keyword{models}{vcov}
\keyword{nonlinear}{vcov}
\begin{Description}\relax
Returns the variance-covariance matrix of the main parameters of
a fitted model object.
\end{Description}
\begin{Usage}
\begin{verbatim}
vcov(object, ...)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{object}] a fitted model object.

\item[\code{...}] additional arguments for method functions.  For the
\code{\LinkA{glm}{glm}} method this can be used to pass a
\code{dispersion} parameter.

\end{ldescription}
\end{Arguments}
\begin{Details}\relax
This is a generic function.
Functions with names beginning in \code{vcov.} will be
methods for this function.
Classes with methods for this function include:
\code{lm}, \code{mlm}, \code{glm}, \code{nls},
\code{negbin}, \code{polr}, \code{rlm} (in package \pkg{MASS}),
\code{multinom} (in package \code{nnet})
\code{gls}, \code{lme} (in package \pkg{nlme},
\code{coxph} and \code{survreg} (in package \pkg{survival}).
\end{Details}
\begin{Value}
A matrix of the estimated covariances between the parameter estimates
in the linear or non-linear predictor of the model.
\end{Value}

