\Header{screen}{Creating and Controlling Multiple Screens on a Single Device}
\alias{close.screen}{screen}
\alias{erase.screen}{screen}
\alias{split.screen}{screen}
\keyword{aplot}{screen}
\keyword{dplot}{screen}
\keyword{device}{screen}
\begin{Description}\relax
\code{split.screen} defines a number of regions within the current
device which can, to some extent, be treated as separate graphics
devices.  It is useful for generating multiple plots on a single
device.  Screens can themselves be split, allowing for quite complex
arrangements of plots.

\code{screen} is used to select which screen to draw in.

\code{erase.screen} is used to clear a single screen.

\code{close.screen} removes the specified screen definition(s).\end{Description}
\begin{Usage}
\begin{verbatim}
split.screen(figs, screen = <<see below>>, erase = TRUE)
screen(n = <<see below>>, new = TRUE)
erase.screen(n = <<see below>>)
close.screen(n = <<see below>>, all.screens = TRUE)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{figs}] A two-element vector describing the number of rows and the
number of columns in a screen matrix \emph{or} a matrix with 4 columns.
If a matrix, then each row describes a screen with values for the left,
right, bottom, and top of the screen (in that order) in NDC units.
\item[\code{n}] A number indicating which screen to prepare for drawing
(\code{screen}), erase (\code{erase.screen}), or close
(\code{close.screen}).
\item[\code{new}] A logical value indicating whether the screen should be
erased as part of the preparation for drawing in the screen.
\item[\code{all.screens}] A logical value indicating whether all of the
screens should be closed.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
The first call to \code{split.screen} places \R{} into split-screen
mode.  The other split-screen functions only work within this mode.
While in this mode, certain other commands should be avoided (see WARNINGS
below).  Split-screen mode is exited by the command 
\code{close.screen(all = TRUE)}\end{Details}
\begin{Value}
\code{split.screen} returns a vector of screen numbers for the
newly-created screens.  With no arguments, \code{split.screen} returns
a vector of valid screen numbers.

\code{screen} invisibly returns the number of the selected screen.
With no arguments, \code{screen} returns the number of the current
screen.

\code{close.screen} returns a vector of valid screen numbers.

\code{screen}, \code{erase.screen}, and \code{close.screen} all return
\code{FALSE} if \R{} is not in split-screen mode.\end{Value}
\begin{Section}{Warning}
These functions are totally incompatible with the
other mechanisms for arranging plots on a device:  \code{par(mfrow)},
\code{par(mfcol)}, and \code{layout()}.  

The functions are also incompatible with some plotting functions, 
such as \code{coplot}, which make use of these other mechanisms.

The functions should not be used with multiple devices.\end{Section}
\begin{SeeAlso}\relax
\code{\Link{par}}, \code{\Link{layout}}, \code{\Link{Devices}},
\code{dev.*}\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
if (interactive()) {
split.screen(c(2,1))             # split display into two screens
split.screen(c(1,3), screen = 2) # now split the bottom half into 3
screen(1) # prepare screen 1 for output
plot(10:1)
screen(4) # prepare screen 4 for output
plot(10:1)
close.screen(all = TRUE) # exit split-screen mode

split.screen(c(2,1))        # split display into two screens
split.screen(c(1,2),2)      # split bottom half in two
plot(1:10)                  # screen 3 is active, draw plot
erase.screen()              #forgot label, erase and redraw
plot(1:10, ylab= "ylab 3")
screen(1)                 # prepare screen 1 for output
plot(1:10)
screen(4)                 # prepare screen 4 for output
plot(1:10, ylab="ylab 4")
screen(1, FALSE)              #return to screen 1, but do not clear
plot(10:1, axes=F, lty=2, ylab="")  # overlay second plot
axis(4)                   # add tic marks to right-hand axis
title("Plot 1")
close.screen(all = TRUE) # exit split-screen mode
}
\end{ExampleCode}
\end{Examples}

