Revision cfbcc7dcf1726af32c52afc198eaf99a6c802ec5 authored by Adrian Baddeley on 01 June 2015, 07:46:50 UTC, committed by cran-robot on 01 June 2015, 07:46:50 UTC
1 parent cdb30ea
linnet.Rd
\name{linnet}
\alias{linnet}
\title{
Create a Linear Network
}
\description{
Creates an object of class \code{"linnet"} representing
a network of line segments.
}
\usage{
linnet(vertices, m, edges, sparse=FALSE)
}
\arguments{
\item{vertices}{
Point pattern (object of class \code{"ppp"})
specifying the vertices of the network.
}
\item{m}{
Adjacency matrix. A matrix or sparse matrix
of logical values equal to \code{TRUE}
when the corresponding vertices are joined by a line.
(Specify either \code{m} or \code{edges}.)
}
\item{edges}{
Edge list. A two-column matrix of integers,
specifying all pairs of vertices
that should be joined by an edge.
(Specify either \code{m} or \code{edges}.)
}
\item{sparse}{
Optional. Logical value indicating whether to use a
sparse matrix representation of the network. See Details.
}
}
\details{
An object of class \code{"linnet"} represents a network of
straight line segments in two dimensions. The function \code{linnet} creates
such an object from the minimal information: the spatial location
of each vertex (endpoint, crossing point or meeting point of lines)
and information about which vertices are joined by an edge.
If \code{sparse=FALSE} (the default), the algorithm will compute
and store various properties of the network, including
the adjacency matrix \code{m} and a matrix giving the
shortest-path distances between each pair of vertices in the network.
This is more efficient for small datasets. However it can require
large amounts of memory and can take a long time to execute.
If \code{sparse=TRUE}, then the shortest-path distances will not be computed,
and the network adjacency matrix \code{m} will be stored as a
sparse matrix. This saves a lot of time and memory when creating the
linear network.
}
\value{
Object of class \code{"linnet"} representing the linear network.
}
\author{
Ang Qi Wei \email{aqw07398@hotmail.com} and
Adrian Baddeley \email{Adrian.Baddeley@uwa.edu.au}
\url{http://www.maths.uwa.edu.au/~adrian/}
}
\seealso{
\code{\link{simplenet}} for an example of a linear network.
\code{\link[spatstat:methods.linnet]{methods.linnet}} for
methods applicable to \code{linnet} objects.
\code{\link{delaunayNetwork}}.
\code{\link{ppp}},
\code{\link{psp}}.
}
\examples{
# letter 'A' specified by adjacency matrix
v <- ppp(x=(-2):2, y=3*c(0,1,2,1,0), c(-3,3), c(-1,7))
m <- matrix(FALSE, 5,5)
for(i in 1:4) m[i,i+1] <- TRUE
m[2,4] <- TRUE
m <- m | t(m)
letterA <- linnet(v, m)
plot(letterA)
# letter 'A' specified by edge list
edg <- cbind(1:4, 2:5)
edg <- rbind(edg, c(2,4))
letterA <- linnet(v, edges=edg)
}
\keyword{spatial}
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