vcov.mppm.Rd
\name{vcov.mppm}
\alias{vcov.mppm}
\title{Calculate Variance-Covariance Matrix for Fitted Multiple Point
Process Model}
\description{
Given a fitted multiple point process model, calculate the
variance-covariance matrix of the parameter estimates.
}
\usage{
\method{vcov}{mppm}(object, ..., what="vcov", err="fatal")
}
\arguments{
\item{object}{
A multiple point process model (object of class \code{"mppm"}).
}
\item{\dots}{
Arguments recognised by \code{\link{vcov.ppm}}.
}
\item{what}{
Character string indicating which quantity should be calculated.
Options include \code{"vcov"} for the variance-covariance matrix,
\code{"corr"} for the correlation matrix, and \code{"fisher"}
for the Fisher information matrix.
}
\item{err}{
Character string indicating what action to take if an error occurs.
Either \code{"fatal"}, \code{"warn"} or \code{"null"}.
}
}
\details{
This is a method for the generic function \code{\link{vcov}}.
The argument \code{object} should be a fitted multiple point process
model (object of class \code{"mppm"}) generated by \code{\link{mppm}}.
The variance-covariance matrix of the parameter estimates
is computed using asymptotic theory for maximum likelihood
(for Poisson processes) or estimating equations (for other Gibbs models).
If \code{what="vcov"} (the default), the variance-covariance matrix
is returned.
If \code{what="corr"}, the variance-covariance matrix is normalised
to yield a correlation matrix, and this is returned.
If \code{what="fisher"}, the Fisher information matrix is returned instead.
In all three cases, the rows and columns of the matrix correspond
to the parameters (coefficients) in the same order as in
\code{coef{model}}.
If errors or numerical problems occur, the
argument \code{err} determines what will happen. If
\code{err="fatal"} an error will occur. If \code{err="warn"}
a warning will be issued and \code{NA} will be returned.
If \code{err="null"}, no warning is issued, but \code{NULL} is returned.
}
\value{
A numeric matrix (or \code{NA} or \code{NULL}).
}
\section{Error messages}{
An error message that reports
\emph{system is computationally singular} indicates that the
determinant of the Fisher information matrix of one of the models
was either too large or too small for reliable numerical calculation.
See \code{\link{vcov.ppm}} for suggestions on how to handle this.
}
\seealso{
\code{\link{vcov}}, \code{\link{vcov.ppm}},
\code{\link{mppm}}
}
\examples{
fit <- mppm(Wat ~x, data=hyperframe(Wat=waterstriders))
vcov(fit)
}
\references{
Baddeley, A., Rubak, E. and Turner, R. (2015)
\emph{Spatial Point Patterns: Methodology and Applications with R}.
London: Chapman and Hall/CRC Press.
}
\author{
Adrian Baddeley, Ida-Maria Sintorn and Leanne Bischoff.
Implemented by
\spatstatAuthors.
}
\keyword{spatial}
\keyword{methods}
\keyword{models}