\Header{print.trellis}{Print Trellis Objects}
\keyword{hplot}{print.trellis}
\begin{Description}\relax
Print (plot) a trellis object.
\end{Description}
\begin{Usage}
\begin{verbatim}
## S3 method for class 'trellis':
print(x, position, split,
     more = FALSE, newpage = TRUE,
     panel.height = list(1, "null"),
     panel.width = list(1, "null"),
     ...)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{x}] The object to be plotted, of class ``trellis''
\item[\code{position}] a vector of 4 numbers, typically c(xmin, ymin, xmax,
ymax) that give the lower-left and upper-right corners of a
rectangle in which the Trellis plot of x is to be positioned. The
coordinate system for this rectangle is [0-1] in both the x and y
directions.

\item[\code{split}] a vector of 4 integers, c(x,y,nx,ny) , that says to
position the current plot at the x,y position in a regular array of
nx by ny plots. (Note: this has origin at top left)

\item[\code{more}] A logical specifying whether more plots will follow on
this page.

\item[\code{newpage}] A logical specifying whether the plot should be on a
new page. This option is specific to lattice, and is useful for
including lattice plots in an arbitrary grid viewport (see the
details section).

\item[\code{panel.width, panel.height}] lists with 2 components, that should
be valid \code{x} and \code{units} arguments to \code{unit()} (the
\code{data} argument cannot be specified currently, but can be
considered for addition if needed). The resulting \code{unit} object
will be the width/height of each panel in the Lattice plot. These
arguments can be used to explicitly control the dimensions of the
panel, rather than letting them expand to maximize available space.

Note that this option should not be used in conjunction with
non-default values of the \code{aspect} argument in the original
high level call (no error will be produced, but the resulting
behaviour is undefined).

\item[\code{...}] extra arguments, ignored
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
This is the default print method for objects of class
\code{"trellis"}, produced by calls to functions like \code{xyplot,
    bwplot} etc. It is usually called automatically when a trellis
object is produced. It can also be called explicitly to control plot
positioning by means of the arguments \code{split} and
\code{position}.

When \code{newpage = FALSE}, the current grid viewport is treated as
the plotting area, making it possible to embed a Lattice plot inside
an arbitrary grid viewport.

The print method uses the information in \code{x} (the object to be
printed) to produce a display using the Grid graphics engine. At the
heart of the plot is a grid layout, of which the entries of most
interest to the user are the ones containing the display panels.

Unlike in older versions of Lattice (and Grid), the grid display tree
is retained after the plot is produced, making it possible to access
individual viewport locations and make additions to the plot. The full
tree can be viewed using the grid function
\code{\Link{current.vpTree}}, and individual
viewports can be `seeked' using
\code{\Link{seekViewport}}.  The viewports that
correspond to panels (which is what the user would be interested in)
have names of the form \code{panel.n}, where \code{n} is a simple
incremental counter for the panels. These names can be used in
\code{seekViewport}. For multi-page displays, only the viewports for
the last page are available.  This functionality is still very new,
and details may change in the future.
\end{Details}
\begin{Note}\relax
Trying to position multipage displays will mess things up.
\end{Note}
\begin{Author}\relax
Deepayan Sarkar \email{deepayan@stat.wisc.edu}
\end{Author}
\begin{SeeAlso}\relax
\code{\Link{Lattice}}, \code{\Link{unit}}
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
data(singer)
p11 <- histogram( ~ height | voice.part, data = singer, xlab="Height")
p12 <- densityplot( ~ height | voice.part, data = singer, xlab = "Height")
p2 <- histogram( ~ height, data = singer, xlab = "Height")
data(sunspot)
p3 <- xyplot(sunspot~1:37, aspect="xy", type = "l")
## simple positioning by split
print(p11, split=c(1,1,1,2), more=TRUE)
print(p2, split=c(1,2,1,2))

## Combining split and position:
print(p11, position = c(0,0,.75,.75), split=c(1,1,1,2), more=TRUE)
print(p12, position = c(0,0,.75,.75), split=c(1,2,1,2), more=TRUE)
print(p3, position = c(.5,.75,1,1), more=FALSE)

## Using seekViewport
data(longley)

## repeat same plot, with different polynomial fits in each panel
xyplot(Armed.Forces ~ Year, longley, index.cond = list(rep(1, 6)),
       panel = function(x, y, panel.counter, ...)
       {
           panel.xyplot(x, y, ...)
           fm <- lm(y ~ poly(x, panel.counter))
           llines(x, predict(fm))
       })

## Not run: 
grid::seekViewport("panel.1")
cat("Click somewhere inside the first panel:\n")
ltext(grid::grid.locator(), lab = "linear")
## End(Not run)

grid::seekViewport("panel.1")
grid::grid.text("linear")

grid::seekViewport("panel.2")
grid::grid.text("quadratic")

grid::seekViewport("panel.3")
grid::grid.text("cubic")

grid::seekViewport("panel.4")
grid::grid.text("degree 4")

grid::seekViewport("panel.5")
grid::grid.text("degree 5")

grid::seekViewport("panel.6")
grid::grid.text("degree 6")
\end{ExampleCode}
\end{Examples}

