\name{rjitter}
\alias{rjitter}
\title{Random Perturbation of a Point Pattern}
\description{
Applies independent random displacements to each point in a point pattern.
}
\usage{
rjitter(X, radius, retry=TRUE, giveup = 10000)
}
\arguments{
\item{X}{
A point pattern (object of class \code{"ppp"}).
}
\item{radius}{
Scale of perturbations. A positive numerical value.
The displacement vectors will be uniformly
distributed in a circle of this radius.
}
\item{retry}{
What to do when a perturbed point lies outside the window
of the original point pattern. If \code{retry=FALSE},
the point will be lost; if \code{retry=TRUE},
the algorithm will try again.
}
\item{giveup}{
Maximum number of unsuccessful attempts.
}
}
\details{
Each of the points in the point pattern \code{X} is subjected to
an independent random displacement. The displacement vectors are
uniformly distributed in a circle of radius \code{radius}.
If a displaced point lies outside the window, then if
\code{retry=FALSE} the point will be lost.
However if \code{retry=TRUE}, the algorithm will try again: each time a
perturbed point lies outside the window, the algorithm will reject it and
generate another proposed perturbation of the original point,
until one lies inside the window, or until \code{giveup} unsuccessful
attempts have been made. In the latter case, any unresolved points
will be included without any perturbation. The return value will
always be a point pattern with the same number of points as \code{X}.
}
\value{
A point pattern (object of class \code{"ppp"}) in the same window
as \code{X}.
}
\examples{
X <- rsyst(owin(), 10, 10)
Y <- rjitter(X, 0.02)
plot(Y)
}
\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{datagen}