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\name{sampleRegular}
\alias{sampleRegular}
\alias{sampleRegular,Raster-method}
\title{Regular sample}
\description{
Take a systematic sample from a Raster* object.
}
\usage{
\S4method{sampleRegular}{Raster}(x, size, ext=NULL, cells=FALSE, xy=FALSE, asRaster=FALSE,
sp=FALSE, ...)
}
\arguments{
\item{x}{Raster object}
\item{size}{positive integer giving the number of items to choose.}
\item{ext}{Extent. To limit regular sampling to the area within that box}
\item{cells}{logical. Also return sampled cell numbers (if asRaster=FALSE) }
\item{xy}{logical. If \code{TRUE}, coordinates of sampled cells are also returned}
\item{asRaster}{logical. If \code{TRUE}, a RasterLayer or RasterBrick is returned, rather than the sampled values}
\item{sp}{logical. If \code{TRUE}, a SpatialPointsDataFrame is returned}
\item{...}{additional arguments. None implemented}
}
\value{
A vector (single layer object), matrix (multi-layered object; or if \code{cells=TRUE}, or \code{xy=TRUE}), Raster* object (if \code{asRaster=TRUE}), or SpatialPointsDataFrame (if \code{sp=TRUE})
}
\seealso{\code{\link{sampleRandom}}, \link{sampleStratified}}
\examples{
r <- raster(system.file("external/test.grd", package="raster"))
v <- sampleRegular(r, size=100)
x <- sampleRegular(r, size=100, asRaster=TRUE)
}
\keyword{spatial}
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