as.psp.Rd
\name{as.psp}
\alias{as.psp}
\alias{as.psp.psp}
\alias{as.psp.data.frame}
\alias{as.psp.matrix}
\alias{as.psp.owin}
\alias{as.psp.default}
\title{Convert Data To Class psp}
\description{
Tries to coerce any reasonable kind of data to a line segment pattern
(an object of class \code{"psp"})
for use by the \pkg{spatstat} package.
}
\usage{
as.psp(x, \dots, from=NULL, to=NULL)
\method{as.psp}{psp}(x, \dots, fatal=TRUE)
\method{as.psp}{data.frame}(x, \dots, window=NULL, marks=NULL, fatal=TRUE)
\method{as.psp}{matrix}(x, \dots, window=NULL, marks=NULL, fatal=TRUE)
\method{as.psp}{owin}(x, \dots, fatal=TRUE)
\method{as.psp}{default}(x, \dots, window=NULL, marks=NULL, fatal=TRUE)
}
\arguments{
\item{x}{Data which will be converted into a line segment pattern}
\item{window}{Data which define a window for the pattern
when \code{x} does not contain a window}
\item{\dots}{Ignored.}
\item{marks}{(Optional) vector of marks for the pattern}
\item{fatal}{Logical value. See Details.}
\item{from,to}{Point patterns (object of class \code{"ppp"})
containing the first and second endpoints (respectively) of each
segment. Incompatible with \code{x}.
}
}
\value{
An object of class \code{"psp"} (see \code{\link{psp.object}})
describing the line segment pattern and its window of observation.
The value \code{NULL} may also be returned; see Details.
}
\details{
Converts the dataset \code{x} to a line segment pattern
(an object of class \code{"psp"}; see \code{\link{psp.object}} for
an overview).
This function is normally used to convert an existing line segment pattern
dataset, stored in another format, to the \code{"psp"} format.
To create a new point pattern from raw data such as \eqn{x,y}
coordinates, it is normally easier to use the creator function
\code{\link{psp}}.
The dataset \code{x} may be:
\itemize{
\item
an object of class \code{"psp"}
\item
a data frame with columns named \code{x0, y0, x1, y1}
that will be interpreted as the coordinates of the endpoints
of the segments
\item
a data frame or matrix with exactly 4 columns
that will be interpreted as the coordinates \code{x0, y0, x1, y1}
of the endpoints of the segments
\item
a data frame with columns named \code{xmid, ymid, length, angle}
that will be interpreted as the coordinates of the segment
midpoints, the lengths of the segments, and the orientations of the
segments in radians
\item
a structure with elements named \code{x0, y0, x1, y1}
or elements named \code{xmid, ymid, length, angle}
which will be interpreted as above.
\item
an object of class \code{"owin"} representing a spatial window;
it must be of type \code{"rectangle"} or \code{"polygonal"}.
The boundary edges of the window will be extracted as a line segment
pattern.
}
Alternatively, you may specify two point patterns
\code{from} and \code{to} containing the first and second endpoints
of the line segments.
The argument \code{window} is converted to a window object
by the function \code{\link{as.owin}}.
The argument \code{fatal} indicates what to do when
the data cannot be converted to a line segment pattern.
If \code{fatal=TRUE}, a fatal error
will be generated; if \code{fatal=FALSE}, the
value \code{NULL} is returned.
The function \code{as.psp} is generic, with methods for the
classes \code{"psp"}, \code{"data.frame"}, \code{"matrix"}
and a default method.
Point pattern datasets can also be created by the function
\code{\link{psp}}.
}
\seealso{
\code{\link{psp}},
\code{\link{psp.object}},
\code{\link{as.owin}},
\code{\link{owin.object}}
}
\examples{
mat <- matrix(runif(40), ncol=4)
a <- as.psp(mat, window=owin())
stuff <- list(xmid=runif(10),
ymid=runif(10),
length=rep(0.1, 10),
angle=runif(10, 0, 2 * pi))
a <- as.psp(stuff, window=owin())
b <- as.psp(from=runifpoint(10), to=runifpoint(10))
}
\author{Adrian Baddeley
\email{adrian@maths.uwa.edu.au}
\url{http://www.maths.uwa.edu.au/~adrian/}
and Rolf Turner
\email{r.turner@auckland.ac.nz}
}
\keyword{spatial}
\keyword{manip}