vertices.Rd
\name{vertices}
\alias{vertices}
\alias{vertices.owin}
\title{Vertices of a Window}
\description{
Finds the vertices of a window, or similar object.
}
\usage{
vertices(w)
\method{vertices}{owin}(w)
}
\arguments{
\item{w}{A window (object of class \code{"owin"}) or similar object.}
}
\value{
A list with components \code{x} and \code{y} giving the coordinates
of the vertices.
}
\details{
This function computes the vertices (`corners') of a spatial window
or other object.
For \code{vertices.owin},
the argument \code{w} should be a window (an object of class
\code{"owin"}, see \code{\link{owin.object}} for details).
If \code{w} is a rectangle, the coordinates of the
four corner points are returned.
If \code{w} is a polygonal window (consisting of one or more
polygons), the coordinates of the vertices of all polygons are
returned.
If \code{w} is a binary mask, then a `boundary pixel' is defined to be
a pixel inside the window
which has at least one neighbour outside the window. The coordinates
of the centres of all boundary pixels are returned.
}
\seealso{
\code{\link{owin.object}}.
}
\examples{
data(letterR)
vert <- vertices(letterR)
plot(letterR, main="Polygonal vertices")
points(vert)
plot(letterR, main="Boundary pixels")
points(vertices(as.mask(letterR)))
}
\author{\adrian
and \rolf
}
\keyword{spatial}
\keyword{math}