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\name{as.linnet.psp}
\alias{as.linnet.psp}
\title{
Convert Line Segment Pattern to Linear Network
}
\description{
Converts a line segment pattern to a linear network.
}
\usage{
\method{as.linnet}{psp}(X, \dots, eps, sparse=FALSE)
}
\arguments{
\item{X}{
Line segment pattern (object of class \code{"psp"}).
}
\item{\dots}{
Ignored.
}
\item{eps}{
Optional. Distance threshold. If two segment endpoints
are closer than \code{eps} units apart, they will be treated
as the same point, and will become a single vertex in the
linear network.
}
\item{sparse}{
Logical value indicating whether to use a sparse matrix
representation, as explained in \code{\link{linnet}}.
}
}
\details{
This command converts any collection of line segments into a linear
network by guessing the connectivity of the network,
using the distance threshold \code{eps}.
If any segments in \code{X} cross over each other, they are first
cut into pieces using \code{\link[spatstat.geom]{selfcut.psp}}.
Then any pair of segment endpoints lying closer than \code{eps}
units apart, is treated as a single vertex. The linear network
is then constructed using \code{\link{linnet}}.
It would be wise to check the result by plotting the degree
of each vertex, as shown in the Examples.
If \code{X} has marks, then these are stored in
the resulting linear network \code{Y <- as.linnet(X)},
and can be extracted as \code{marks(as.psp(Y))} or \code{marks(Y$lines)}.
}
\value{
A linear network (object of class \code{"linnet"}).
The result also has an attribute \code{"camefrom"} indicating
the provenance of each line in the resulting network.
For example \code{camefrom[3]=2} means that the third line segment
in the result is a piece of the second segment of \code{X}.
}
\author{
\spatstatAuthors.
}
\seealso{
\code{\link{linnet}}, \code{\link[spatstat.geom]{selfcut.psp}},
\code{\link{methods.linnet}}.
}
\examples{
# make some data
A <- psp(0.09, 0.55, 0.79, 0.80, window=owin())
B <- superimpose(A, as.psp(simplenet))
# convert to a linear network
L <- as.linnet(B)
# check validity
L
plot(L)
text(vertices(L), labels=vertexdegree(L))
# show the pieces that came from original segment number 1
S <- as.psp(L)
(camefrom <- attr(L, "camefrom"))
parts <- which(camefrom == 1)
plot(S[parts], add=TRUE, col="green", lwd=2)
}
\keyword{spatial}
\keyword{manip}
\concept{Linear network}
|
