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\name{which}
\docType{methods}
\alias{Which}
\alias{Which,RasterLayer-method}
\title{Which cells are TRUE?}
\description{
\code{Which} returns a RasterLayer with \code{TRUE} or \code{FALSE} setting cells that are \code{NA} to \code{FALSE} (unless \code{na.rm=FALSE}). If the RasterLayer has numbers, all values that are 0 become \code{FALSE} and all other values become \code{TRUE}. The function can also return the cell numbers that are \code{TRUE}
}
\usage{
\S4method{Which}{RasterLayer}(x, cells=FALSE, na.rm=TRUE, ...)
}
\arguments{
\item{x}{RasterLayer}
\item{cells}{logical. If \code{TRUE}, cell numbers are returned, otherwise a RasterLayer is returned}
\item{na.rm}{logical. If \code{TRUE}, \code{NA} values are treated as \code{FALSE}, otherwise they remain \code{NA} (only when \code{cells=FALSE})}
\item{...}{Additional arguments (none implemented)}
}
\seealso{ \code{\link{which.max}}, \code{\link{which.min}} }
\value{
RasterLayer
}
\examples{
r <- raster(ncol=10, nrow=10)
set.seed(0)
values(r) <- runif(ncell(r))
r[r < 0.2 ] <- 0
r[r > 0.8] <- 1
r[r > 0 & r < 1 ] <- 0.5
Which(r, cells=TRUE)
Which(r > 0.5, cells=TRUE)
s1 <- r > 0.5
s2 <- Which(r > 0.5)
s1[1:15]
s2[1:15]
# this expression
x1 <- Which(r, na.rm=FALSE)
# is the inverse of
x2 <- r==0
}
\keyword{spatial}
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