is.marked.ppp.Rd
\name{is.marked.ppp}
\alias{is.marked.ppp}
\title{Test Whether A Point Pattern is Marked}
\description{
Tests whether a point pattern has ``marks''
attached to the points.
}
\usage{
\method{is.marked}{ppp}(X, na.action="warn", \dots)
}
\arguments{
\item{X}{
Point pattern (object of class \code{"ppp"})
}
\item{na.action}{
String indicating what to do if \code{NA} values are
encountered amongst the marks.
Options are \code{"warn"}, \code{"fatal"} and \code{"ignore"}.
}
\item{\dots}{
Ignored.
}
}
\value{
Logical value, equal to \code{TRUE} if \code{X} is a marked point pattern.
}
\details{
``Marks'' are observations attached to each point of a point pattern.
For example the \code{\link{longleaf}} dataset contains the locations
of trees, each tree being marked by its diameter;
the \code{\link{amacrine}} dataset gives the locations of cells
of two types (on/off) and the type of cell may be regarded as a mark attached
to the location of the cell.
This function tests whether the point pattern \code{X}
contains or involves marked points.
It is a method for the generic function \code{\link{is.marked}}.
The argument \code{na.action} determines what action will be taken
if the point pattern has a vector of marks but some or all of the
marks are \code{NA}. Options are \code{"fatal"} to cause a fatal
error; \code{"warn"} to issue a warning and then return \code{TRUE};
and \code{"ignore"} to take no action except returning \code{TRUE}.
}
\seealso{
\code{\link{is.marked}},
\code{\link{is.marked.ppm}}
}
\examples{
data(cells)
is.marked(cells) #FALSE
data(longleaf)
is.marked(longleaf) #TRUE
}
\author{\adrian
and \rolf
}
\keyword{spatial}
\keyword{manip}