\HeaderA{strip.default}{Default Trellis Strip Function}{strip.default}
\aliasA{strip.custom}{strip.default}{strip.custom}
\keyword{dplot}{strip.default}
\begin{Description}\relax
\code{strip.default} is the function that draws the strips by default
in Trellis plots.  Users can write their own strip functions, but most
commonly this involves calling \code{strip.default} with a slightly
different arguments.  \code{strip.custom} provides a convenient way to
obtain new strip functions that differ from \code{strip.default} only
in the default values of certain arguments.
\end{Description}
\begin{Usage}
\begin{verbatim}
strip.default(which.given,
              which.panel,
              packet.number,
              panel.number,
              var.name,
              factor.levels,
              shingle.intervals,
              strip.names = c(FALSE, TRUE),
              strip.levels = c(TRUE, FALSE),
              sep = " : ",
              style = 1,
              horizontal = TRUE,
              bg = trellis.par.get("strip.background")$col[which.given],
              fg = trellis.par.get("strip.shingle")$col[which.given],
              par.strip.text = trellis.par.get("add.text"))
strip.custom(...)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{which.given}] integer index specifying which of the conditioning
variables this strip corresponds to. 

\item[\code{which.panel}] vector of integers as long as the number of
conditioning variables. The contents are indices specifying the
current levels of each of the conditioning variables (thus, this
would be unique for each distinct panel).

\item[\code{panel.number, packet.number}] integer indices specifying which
panel and packet is being drawn (see the entry for \code{panel} in
\code{\LinkA{xyplot}{xyplot}} for details).  These arguments are ignored by
the \code{strip.default}, but may be used by user supplied
replacements.

\item[\code{var.name}] vector of character strings or expressions as long as
the number of conditioning variables.  The contents are interpreted
as names for the conditioning variables.  Whether they are shown on
the strip depends on the values of \code{strip.names} and
\code{style} (see below).  By default, the names are shown for
shingles, but not for factors.

\item[\code{factor.levels}] vector of character strings or expressions
giving the levels of the conditioning variable currently being
drawn.  For more than one conditioning variable, this will vary with
\code{which.given}.  Whether these levels are shown on the strip
depends on the values of \code{strip.levels} and \code{style} (see
below).  \code{factor.levels} may be specified for both factors and
shingles (despite the name), but by default they are shown only for
factors.

\item[\code{shingle.intervals}] if the current strip corresponds to a shingle,
this should be a 2-column matrix giving the levels of the shingle.
(of the form that would be produced by \bold{printing}
\code{levels(shingle)}). Otherwise, it should be \code{NULL}

\item[\code{strip.names}] a logical vector of length 2, indicating whether
or not the name of the conditioning variable that corresponds to the
strip being drawn is to be written on the strip. The two components
give the values for factors and shingles respectively.

This argument is ignored for a factor when \code{style} is not one
of 1 and 3.

\item[\code{strip.levels}] a logical vector of length 2, indicating whether
or not the level of the conditioning variable that corresponds to
the strip being drawn is to be written on the strip.  The two
components give the values for factors and shingles respectively.

\item[\code{sep}] character or expression, serving as a separator if the
name and level are both to be shown.

\item[\code{style}] integer, with values 1, 2, 3, 4 and 5 currently
supported, controlling how the current level of a factor is encoded.
Ignored for shingles (actually, when \code{shingle.intervals} is
non-null.  

The best way to find out what effect the value of \code{style} has
is to try them out. Here is a short description: for a style value
of 1, the strip is colored in the background color with the strip
text (as determined by other arguments) centered on it. A value of 3
is the same, except that a part of the strip is colored in the
foreground color, indicating the current level of the factor. For
styles 2 and 4, the part corresponding to the current level remains
colored in the foreground color, however, for style = 2, the
remaining part is not colored at all, whereas for 4, it is colored
with the background color. For both these, the names of all the
levels of the factor are placed on the strip from left to right.
Styles 5 and 6 produce the same effect (they are subtly different in
S, this implementation corresponds to 5), they are similar to style
1, except that the strip text is not centered, it is instead
positioned according to the current level.

Note that unlike S-PLUS, the default value of \code{style} is 1.
\code{strip.names} and \code{strip.levels} have no effect if
\code{style} is not 1 or 3.

\item[\code{horizontal}] logical, specifying whether the labels etc should
be horizontal.  \code{horizontal=FALSE} is useful for strips on the
left of panels using \code{strip.left=TRUE} 
\item[\code{par.strip.text}] list with parameters controlling the text on
each strip, with components \code{col}, \code{cex}, \code{font},
etc.

\item[\code{bg}] strip background color. 
\item[\code{fg}] strip foreground color. 
\item[\code{...}] arguments to be passed on to \code{strip.default}, overriding
whatever value it would have normally assumed

\end{ldescription}
\end{Arguments}
\begin{Details}\relax
default strip function for trellis functions. Useful 
mostly because of the \code{style} argument --- non-default styles
are often more informative, especially when the names of the levels
of the factor \code{x} are small. Traditional use is as
\code{strip = function(...) strip.default(style=2,...)}, though
this can be simplified by the use of \code{strip.custom}.
\end{Details}
\begin{Value}
\code{strip.default} is called for its side-effect, which is to draw a
strip appropriate for multi-panel Trellis conditioning plots.
\code{strip.custom} returns a function that is similar to
\code{strip.default}, but with different defaults for the arguments
specified in the call.
\end{Value}
\begin{Author}\relax
Deepayan Sarkar \email{Deepayan.Sarkar@R-project.org}
\end{Author}
\begin{SeeAlso}\relax
\code{\LinkA{xyplot}{xyplot}}, \code{\LinkA{Lattice}{Lattice}}
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
## Traditional use
xyplot(Petal.Length ~ Petal.Width | Species, iris,
       strip = function(..., style) strip.default(..., style = 4))

## equivalent call using strip.custom
xyplot(Petal.Length ~ Petal.Width | Species, iris,
       strip = strip.custom(style = 4))

xyplot(Petal.Length ~ Petal.Width | Species, iris,
       strip = FALSE,
       strip.left = strip.custom(style = 4, horizontal = FALSE))
\end{ExampleCode}
\end{Examples}

