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\name{approxExtrap}
\alias{approxExtrap}
\title{Linear Extrapolation}
\description{
Works in conjunction with the \code{\link{approx}} function to do linear
extrapolation. \code{\link{approx}} in R does not support extrapolation at
all, and it is buggy in S-Plus 6.
}
\usage{
approxExtrap(x, y, xout, method = "linear", n = 50, rule = 2, f = 0,
ties = "ordered", na.rm = FALSE)
}
\arguments{
\item{x,y,xout,method,n,rule,f}{
see \code{\link{approx}}
}
\item{ties}{
applies only to R. See \code{\link{approx}}
}
\item{na.rm}{
set to \code{TRUE} to remove \code{NA}s in \code{x} and
\code{y} before proceeding
}
}
\details{
Duplicates in \code{x} (and corresponding \code{y} elements) are removed
before using \code{approx}.
}
\value{
a vector the same length as \code{xout}
}
\author{Frank Harrell}
\seealso{\code{\link{approx}}}
\examples{
approxExtrap(1:3,1:3,xout=c(0,4))
}
\keyword{arith}
\keyword{dplot}
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