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\name{lintess}
\alias{lintess}
\title{
Tessellation on a Linear Network
}
\description{
Create a tessellation on a linear network.
}
\usage{
lintess(L, df, marks=NULL)
}
\arguments{
\item{L}{
Linear network (object of class \code{"linnet"}).
}
\item{df}{
Data frame of local coordinates for the pieces that make up the
tiles of the tessellation. See Details.
}
\item{marks}{
Vector or data frame of
marks associated with the tiles of the tessellation.
}
}
\details{
A tessellation on a linear network \code{L} is a partition of the
network into non-overlapping pieces (tiles). Each tile consists of one
or more line segments which are subsets of the line segments making up
the network. A tile can consist of several disjoint pieces.
The data frame \code{df} should have columns named
\code{seg}, \code{t0}, \code{t1} and \code{tile}.
Any additional columns will be ignored.
Each row of the data frame specifies one sub-segment of the network
and allocates it to a particular tile.
The \code{seg} column specifies which line segment of the network
contains the sub-segment. Values of \code{seg} are integer indices
for the segments in \code{as.psp(L)}.
The \code{t0} and \code{t1} columns specify the start and end points
of the sub-segment. They should be numeric values between 0 and 1
inclusive, where the values 0 and 1 representing the network vertices
that are joined by this network segment.
The \code{tile} column specifies which tile of the tessellation
includes this sub-segment. It will be coerced to a factor and its
levels will be the names of the tiles.
If \code{df} is missing or \code{NULL}, the result is a tessellation
with only one tile, consisting of the entire network \code{L}.
Additional data called \emph{marks} may be associated with
each tile of the tessellation. The argument \code{marks} should be
a vector with one entry for each tile (that is, one entry for each
level of \code{df$tile}) or a data frame with one row for each tile.
In general \code{df} and \code{marks} will have different numbers of rows.
}
\value{
An object of class \code{"lintess"}.
There are methods for \code{print}, \code{plot} and
\code{summary} for this object.
}
\author{
\adrian and Greg McSwiggan.
}
\seealso{
\code{\link{linnet}} for linear networks.
\code{\link{plot.lintess}} for plotting.
\code{\link{divide.linnet}} to make a tessellation demarcated by
given points.
\code{\link{chop.linnet}} to make a tessellation demarcated by
infinite lines.
\code{\link{lineardirichlet}} to create the Dirichlet-Voronoi
tessellation from a point pattern on a linear network.
\code{\link{as.linfun.lintess}}, \code{\link{as.linnet.lintess}} and
\code{\link{as.linim}} to convert to other classes.
\code{\link{tile.lengths}} to compute the length of each tile
in the tessellation.
The undocumented methods \code{Window.lintess} and
\code{as.owin.lintess} extract the spatial window.
}
\examples{
# tessellation consisting of one tile for each existing segment
ns <- nsegments(simplenet)
df <- data.frame(seg=1:ns, t0=0, t1=1, tile=letters[1:ns])
u <- lintess(simplenet, df)
u
plot(u)
S <- as.psp(simplenet)
marks(u) <- data.frame(len=lengths_psp(S), ang=angles.psp(S))
u
plot(u)
}
\keyword{spatial}
\keyword{datagen}
\concept{Tessellation}
\concept{Linear network}
|
