Revision d606122dc24b56ecf537d55eda38f4bf5ac4de1f authored by Adrian Baddeley on 25 October 2010, 10:40:51 UTC, committed by cran-robot on 25 October 2010, 10:40:51 UTC
1 parent 66bc933
gridcentres.Rd
\name{gridcentres}
\alias{gridcentres}
\alias{gridcenters}
\title{Rectangular grid of points}
\description{
Generates a rectangular grid of points in a window
}
\usage{
gridcentres(window, nx, ny)
}
\arguments{
\item{window}{A window.
An object of class \code{\link{owin}},
or data in any format acceptable to \code{\link{as.owin}()}.
}
\item{nx}{Number of points
in each row of the rectangular grid.
}
\item{ny}{Number of points
in each column of the rectangular grid.
}
}
\value{
A list with two components \code{x} and \code{y}, which are numeric
vectors giving the coordinates of the points of the
rectangular grid.
}
\details{
This function creates a rectangular grid of points in the window.
The bounding rectangle of the \code{window} is divided into
a regular \eqn{nx \times ny}{nx * ny} grid of rectangular tiles.
The function returns the \eqn{x,y} coordinates of the
centres of these tiles.
Note that some of these grid points may lie outside the window,
if \code{window} is not of type \code{"rectangle"}. The function
\code{\link{inside.owin}} can be used to select those grid points
which do lie inside the window. See the examples.
This function is useful in creating dummy points for quadrature
schemes (see \code{\link{quadscheme}}) and for other miscellaneous
purposes.
}
\seealso{
\code{\link{quad.object}},
\code{\link{quadscheme}},
\code{\link{inside.owin}},
\code{\link{stratrand}}
}
\examples{
w <- unit.square()
xy <- gridcentres(w, 10,15)
\dontrun{
plot(w)
points(xy)
}
bdry <- list(x=c(0.1,0.3,0.7,0.4,0.2),
y=c(0.1,0.1,0.5,0.7,0.3))
w <- owin(c(0,1), c(0,1), poly=bdry)
xy <- gridcentres(w, 30, 30)
ok <- inside.owin(xy$x, xy$y, w)
\dontrun{
plot(w)
points(xy$x[ok], xy$y[ok])
}
}
\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}
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