transect.im.Rd
\name{transect.im}
\alias{transect.im}
\title{
Pixel Values Along a Transect
}
\description{
Extract the pixel values of a pixel image at each point along
a linear transect.
}
\usage{
transect.im(X, ..., from="bottomleft", to="topright",
click=FALSE, add=FALSE)
}
\arguments{
\item{X}{
A pixel image (object of class \code{"im"}).
}
\item{\dots}{
Ignored.
}
\item{from,to}{
Optional. Start point and end point of the transect.
Pairs of \eqn{(x,y)} coordinates
in a format acceptable to \code{\link{xy.coords}},
or keywords \code{"bottom"}, \code{"left"}, \code{"top"},
\code{"right"}, \code{"bottomleft"} etc.
}
\item{click}{
Optional.
Logical value.
If \code{TRUE}, the linear transect is determined interactively
by the user, who clicks two points on the current plot.
}
\item{add}{
Logical. If \code{click=TRUE}, this argument determines
whether to perform interactive tasks on the current plot (\code{add=TRUE})
or to start by plotting \code{X} (\code{add=FALSE}).
}
}
\details{
The pixel values of the image \code{X} along a line segment
will be extracted. The result is a function table (\code{"fv"} object)
which can be plotted directly.
If \code{click=TRUE}, then the user is prompted to click two points on
the plot of \code{X}. These endpoints define the transect.
Otherwise, the transect is defined by the endpoints
\code{from} and \code{to}. The default is a diagonal transect from
bottom left to top right of the frame.
}
\value{
An object of class \code{"fv"} which can be plotted.
}
\author{
\adrian
and \rolf
}
\seealso{
\code{\link{im}}
}
\examples{
Z <- density(redwood)
plot(transect.im(Z))
\dontrun{
if(FALSE) {
plot(transect.im(Z, click=TRUE))
}
}
}
\keyword{spatial}
\keyword{manip}
\keyword{iplot}