\name{crossdist.psp}
\alias{crossdist.psp}
\title{Pairwise distances between two different line segment patterns}
\description{
  Computes the distances between all pairs of line segments
  taken from two different line segment patterns.
}
\usage{
  \method{crossdist}{psp}(X, Y, \dots, method="Fortran")
}
\arguments{
  \item{X,Y}{
    Line segment patterns (objects of class \code{"psp"}).
  }
  \item{\dots}{
    Ignored.
  }
  \item{method}{String specifying which method of calculation to use.
    Values are \code{"Fortran"} and \code{"interpreted"}.
  }
}
\value{
  A matrix whose \code{[i,j]} entry is the distance
  from the \code{i}-th line segment in \code{X}
  to the \code{j}-th line segment in \code{Y}.
}
\details{
  This is a method for the generic function \code{\link{crossdist}}.

  Given two line segment patterns, 
  this function computes the distance from each line segment
  in the first pattern to each line segment in the second pattern,
  and returns a matrix containing these distances.

  Distances are calculated using the Hausdorff metric.
  The Hausdorff distance between two line segments is the maximum distance
  from any point on one of the segments to the nearest point on
  the other segment.     

  The argument \code{method} is not normally used. It is
  retained only for checking the validity of the software.
  If \code{method = "interpreted"} then the distances are
  computed using interpreted R code only. If \code{method="Fortran"}
  (the default) then Fortran code is used. 
  The Fortran code is several times faster.
}
\seealso{
  \code{\link{pairdist}},
  \code{\link{nndist}},
  \code{\link{Gest}}
}
\examples{
   L1 <- psp(runif(5), runif(5), runif(5), runif(5), owin())
   L2 <- psp(runif(10), runif(10), runif(10), runif(10), owin())
   D <- crossdist(L1, L2)
  #result is a 5 x 10 matrix
}
\author{
  Adrian Baddeley
  \email{adrian@maths.uwa.edu.au}
  \url{http://www.maths.uwa.edu.au/~adrian/}
  and Rolf Turner
  \email{rolf@math.unb.ca}
  \url{http://www.math.unb.ca/~rolf}
}
\keyword{spatial}

\keyword{math}