\HeaderA{banking}{Banking}{banking}
\keyword{dplot}{banking}
\begin{Description}\relax
Calculates banking slope
\end{Description}
\begin{Usage}
\begin{verbatim}
banking(dx, dy)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{dx, dy}] vector of consecutive x, y differences. 
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
\code{banking} is the banking function used when
\code{aspect = "xy"} in high level Trellis functions. It is usually not
very meaningful except with \code{xyplot}.  It considers the
absolute slopes (based on \code{dx} and \code{dy}) and returns a value
which when adjusted by the panel scale limits will make the median of
the above absolute slopes correspond to a 45 degree line.

This function was inspired by the discussion of banking in the
documentation for Trellis Graphics available at Bell Labs' website
(see \code{\LinkA{Lattice}{Lattice}}), but is most likely identical to an
algorithm described by Cleveland et al (see below).  It is
not clear (to the author) whether this is the algorithm used in
S-PLUS.  Alternative banking rules, implemented as a similar function,
can be used as a drop-in replacement by suitably modifying
\code{lattice.options("banking")}.
\end{Details}
\begin{Author}\relax
Deepayan Sarkar \email{Deepayan.Sarkar@R-project.org}
\end{Author}
\begin{References}\relax
Cleveland, William S.,  McGill, Marylyn E. and McGill, Robert (1988),
"The Shape Parameter of a Two-variable Graph",
\emph{Journal of the American Statistical Association}, 83, 289-300
\end{References}
\begin{SeeAlso}\relax
\code{\LinkA{Lattice}{Lattice}}, \code{\LinkA{xyplot}{xyplot}}
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}

xyplot(sunspot.year ~ time(sunspot.year) | equal.count(time(sunspot.year)), 
       xlab = "", type = "l", aspect = "xy", strip = FALSE,
       scales = list(x = list(alternating = 2, relation = "sliced")),
       as.table = TRUE, main = "Yearly Sunspots")

\end{ExampleCode}
\end{Examples}

