model.matrix.ppm.Rd
\name{model.matrix.ppm}
\alias{model.matrix.ppm}
\alias{model.matrix.kppm}
\alias{model.matrix.dppm}
\alias{model.matrix.lppm}
\title{Extract Design Matrix from Point Process Model}
\description{
Given a point process model that has been
fitted to spatial point pattern data,
this function extracts the design matrix of the model.
}
\usage{
\method{model.matrix}{ppm}(object,
data=model.frame(object, na.action=NULL),
\dots,
Q=NULL, keepNA=TRUE)
\method{model.matrix}{kppm}(object,
data=model.frame(object, na.action=NULL),
\dots,
Q=NULL, keepNA=TRUE)
\method{model.matrix}{dppm}(object,
data=model.frame(object, na.action=NULL),
\dots,
Q=NULL, keepNA=TRUE)
\method{model.matrix}{lppm}(object,
data=model.frame(object, na.action=NULL),
\dots,
keepNA=TRUE)
}
\arguments{
\item{object}{
The fitted point process model. An object of class \code{"ppm"}
or \code{"kppm"} or \code{"dppm"} or \code{"lppm"}.
}
\item{data}{
A model frame, containing the data required for the Berman-Turner device.
}
\item{Q}{
A point pattern (class \code{"ppp"}) or quadrature scheme
(class \code{"quad"}) specifying new locations where the
covariates should be computed.
}
\item{keepNA}{
Logical. Determines whether rows containing NA values will be
deleted or retained.
}
\item{\dots}{
Other arguments (such as \code{na.action}) passed to
\code{\link{model.matrix.lm}}.
}
}
\details{
These commands are methods for the generic function
\code{\link{model.matrix}}.
They extract the design matrix of a spatial point process model
(class \code{"ppm"} or \code{"kppm"} or \code{"dppm"}
or \code{"lppm"}).
More precisely, this command extracts
the design matrix of the generalised linear model associated with
a spatial point process model.
The \code{object} must be a fitted point process model
(object of class \code{"ppm"} or \code{"kppm"}
or \code{"dppm"} or \code{"lppm"})
fitted to spatial point pattern data.
Such objects are produced by the model-fitting
functions \code{\link{ppm}}, \code{\link{kppm}}, \code{\link{dppm}}
and \code{\link{lppm}}.
The methods \code{model.matrix.ppm},
\code{model.matrix.kppm}, \code{model.matrix.dppm}
and \code{model.matrix.lppm}
extract the model matrix for the GLM.
The result is a matrix, with one row for every quadrature point
in the fitting procedure, and one column for every constructed
covariate in the design matrix.
If there are \code{NA} values in the covariates,
the argument \code{keepNA} determines whether to retain or delete
the corresponding rows of the model matrix. The default
\code{keepNA=TRUE} is to retain them. Note that this differs from
the default behaviour of many other methods for \code{model.matrix},
which typically delete rows containing \code{NA}.
The quadrature points themselves can be extracted using
\code{\link{quad.ppm}}.
}
\value{
A matrix. Columns of the matrix are covariates in the model.
Rows of the matrix correspond to quadrature points
in the fitting procedure (provided \code{keepNA=TRUE}).
}
\author{
\spatstatAuthors.
}
\seealso{
\code{\link{model.matrix}},
\code{\link{model.images}},
\code{\link{ppm}},
\code{\link{kppm}},
\code{\link{dppm}},
\code{\link{lppm}},
\code{\link{ppm.object}},
\code{\link{quad.ppm}},
\code{\link{residuals.ppm}}
}
\examples{
fit <- ppm(cells ~ x)
head(model.matrix(fit))
model.matrix(fit, Q=runifpoint(5))
kfit <- kppm(redwood ~ x, "Thomas")
m <- model.matrix(kfit)
}
\keyword{spatial}
\keyword{models}