\HeaderA{panel.qqmathline}{Useful panel function with qqmath}{panel.qqmathline}
\keyword{dplot}{panel.qqmathline}
\begin{Description}\relax
Useful panel function with qqmath. Draws a line passing through the
points (usually) determined by the .25 and .75 quantiles of the sample
and the theoretical distribution.
\end{Description}
\begin{Usage}
\begin{verbatim}
panel.qqmathline(x, y = x,
                 distribution = qnorm,
                 p = c(0.25, 0.75),
                 qtype = 7,
                 groups = NULL, 
                 ...)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{x}] The original sample, possibly reduced to a fewer number of
quantiles, as determined by the \code{f.value} argument to
\code{qqmath}

\item[\code{y}] an alias for \code{x} for backwards compatibility

\item[\code{distribution}] quantile function for reference theoretical distribution.

\item[\code{p}] numeric vector of length two, representing probabilities.
Corresponding quantile pairs define the line drawn.

\item[\code{qtype}] the \code{type} of quantile computation used in
\code{\LinkA{quantile}{quantile}}

\item[\code{groups}] optional grouping variable.  If non-null, a line will be drawn for
each group.

\item[\code{...}] other arguments.
\end{ldescription}
\end{Arguments}
\begin{Author}\relax
Deepayan Sarkar \email{Deepayan.Sarkar@R-project.org}
\end{Author}
\begin{SeeAlso}\relax
\code{\LinkA{prepanel.qqmathline}{prepanel.qqmathline}},
\code{\LinkA{qqmath}{qqmath}},
\code{\LinkA{quantile}{quantile}}
\end{SeeAlso}

