Revision 9fc33b4ac23fdcf8e2e93aacb1e9fc5842d57bf3 authored by Adrian Baddeley on 18 December 2007, 00:00:00 UTC, committed by Gabor Csardi on 18 December 2007, 00:00:00 UTC
1 parent 6db367d
runifpoint.Rd
\name{runifpoint}
\alias{runifpoint}
\title{Generate N Uniform Random Points}
\description{
Generate a random point pattern
containing \eqn{n} independent uniform random points.
}
\usage{
runifpoint(n, win=owin(c(0,1),c(0,1)), giveup=1000)
}
\arguments{
\item{n}{
Number of points.
}
\item{win}{
Window in which to simulate the pattern.
An object of class \code{"owin"}
or something acceptable to \code{\link{as.owin}}.
}
\item{giveup}{
Number of attempts in the rejection method after which
the algorithm should stop trying to generate new points.
}
}
\value{
The simulated point pattern (an object of class \code{"ppp"}).
}
\details{
This function generates \code{n} independent random points,
uniformly distributed in the window \code{win}.
(For nonuniform distributions, see \code{\link{rpoint}}.)
The algorithm depends on the type of window, as follows:
\itemize{
\item
If \code{win} is a rectangle then
\eqn{n} independent random points, uniformly distributed
in the rectangle, are generated by assigning uniform random values to their
cartesian coordinates.
\item
If \code{win} is a binary image mask, then a random sequence of
pixels is selected (using \code{\link{sample}})
with equal probabilities. Then for each pixel in the sequence
we generate a uniformly distributed random point in that pixel.
\item
If \code{win} is a polygonal window, the algorithm uses the rejection
method. It finds a rectangle enclosing the window,
generates points in this rectangle, and tests whether they fall in
the desired window. It gives up when \code{giveup * n} tests
have been performed without yielding \code{n} successes.
}
The algorithm for binary image masks is faster than the rejection
method but involves discretisation.
}
\seealso{
\code{\link{ppp.object}},
\code{\link{owin.object}},
\code{\link{rpoispp}},
\code{\link{rpoint}}
}
\examples{
# 100 random points in the unit square
pp <- runifpoint(100)
# irregular window
data(letterR)
# polygonal
pp <- runifpoint(100, letterR)
# binary image mask
pp <- runifpoint(100, as.mask(letterR))
}
\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{datagen}
![swh spinner](/static/img/swh-spinner.gif)
Computing file changes ...