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
hist.im.Rd
\name{hist.im}
\alias{hist.im}
\title{Histogram of Pixel Values in an Image}
\description{
Computes and displays a histogram of the pixel values in a pixel image.
The \code{hist} method for class \code{"im"}.
}
\usage{
\method{hist}{im}(x, \dots, probability=FALSE)
}
\arguments{
\item{x}{A pixel image (object of class \code{"im"}).}
\item{\dots}{Arguments passed to \code{\link{hist.default}}
or \code{\link{barplot}}.}
\item{probability}{Logical. If \code{TRUE}, the histogram will be
normalised to give probabilities or probability densities.
}
}
\details{
This function computes and (by default) displays a histogram
of the pixel values in the image \code{x}.
An object of class \code{"im"}
describes a pixel image. See \code{\link{im.object}})
for details of this class.
The function \code{hist.im} is a method for the generic
function \code{\link{hist}} for the class \code{"im"}.
Any arguments in \code{...} are passed to \code{\link{hist.default}}
(for numeric valued images) or \code{\link{barplot}} (for factor or
logical images).
For example, such arguments control the axes, and may be used to
suppress the plotting.
}
\value{
For numeric-valued images, an object of class \code{"histogram"} as returned
by \code{\link[graphics:hist]{hist.default}}. This object can be
plotted.
For factor-valued or logical images, an object of class
\code{"barplotdata"}, which can be plotted.
This is a list with components
called \code{counts} (contingency table of counts of the numbers of
pixels taking each possible value), \code{probs} (corresponding relative
frequencies) and \code{mids} (graphical \eqn{x}-coordinates of the
midpoints of the bars in the barplot).
}
\seealso{
\code{\link{hist}},
\code{\link{hist.default}},
\code{\link{barplot}},
\code{\link{im.object}},
\code{\link{summary.im}}.
}
\examples{
X <- as.im(function(x,y) {x^2}, unit.square())
hist(X)
hist(cut(X,3))
}
\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{methods}
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