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\name{regLine}
\alias{regLine}
\title{Plot Regression Line}
\description{
Plots a regression line on a scatterplot; the line is plotted
between the minimum and maximum x-values.
}
\usage{
regLine(mod, col=carPalette()[2], lwd=2, lty=1,...)
}
\arguments{
\item{mod}{a model, such as produced by \code{lm},
that responds to the \code{coef} function
by returning a 2-element vector, whose elements are
interpreted respectively as the
intercept and slope of a regresison line.}
\item{col}{color for points and lines; the default is the \emph{second} entry
in the current \pkg{car} palette (see \code{\link{carPalette}}
and \code{\link{par}}).}
\item{lwd}{line width; default is \code{2} (see \code{\link{par}}).}
\item{lty}{line type; default is \code{1}, a solid line (see \code{\link{par}}).}
\item{\dots}{optional arguments to be passed to the
\code{lines} plotting function.}
}
\details{
In contrast to \code{abline}, this function plots only over
the range of the observed x-values. The x-values are extracted from
\code{mod} as the second column of the model matrix.
}
\value{
\code{NULL}. This function is used for its side effect: adding
a line to the plot.
}
\author{John Fox \email{jfox@mcmaster.ca}}
\seealso{\code{\link{abline}}, \code{\link{lines}}}
\examples{
plot(repwt ~ weight, pch=c(1,2)[sex], data=Davis)
regLine(lm(repwt~weight, subset=sex=="M", data=Davis))
regLine(lm(repwt~weight, subset=sex=="F", data=Davis), lty=2)
}
\keyword{aplot}
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