strip.default            package:lattice            R Documentation

Default Trellis Strip Function

Description:

     '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 'strip.default' with a
     slightly different arguments.  'strip.custom' provides a
     convenient way to obtain new strip functions that differ from
     'strip.default' only in the default values of certain arguments.

Usage:

     strip.default(which.given,
                   which.panel,
                   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(...)

Arguments:

which.given: integer index specifying which of the conditioning
          variables this strip corresponds to.  

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 packet).  This is identical
          to the return value of 'which.packet', which is a more
          accurate name. 

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
          'strip.names' and 'style' (see below).  By default, the names
          are shown for shingles, but not for factors. 

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
          'which.given'.  Whether these levels are shown on the strip
          depends on the values of 'strip.levels' and 'style' (see
          below).  'factor.levels' may be specified for both factors
          and shingles (despite the name), but by default they are
          shown only for factors.  If shown, the labels may optionally
          be abbreviated by specifying suitable components in
          'par.strip.text' (see 'xyplot') 

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 *printing*
          'levels(shingle)'). Otherwise, it should be 'NULL' 

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 'style' is not one
          of 1 and 3. 

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. 

     sep: character or expression, serving as a separator if the name
          and level are both to be shown. 

   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 'shingle.intervals' is
          non-null.  

          The best way to find out what effect the value of '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 'style' is 1.
          'strip.names' and 'strip.levels' have no effect if 'style' is
          not 1 or 3. 

horizontal: logical, specifying whether the labels etc should be
          horizontal.  'horizontal=FALSE' is useful for strips on the
          left of panels using 'strip.left=TRUE' 

par.strip.text: list with parameters controlling the text on each
          strip, with components 'col', 'cex', 'font', etc. 

      bg: strip background color. 

      fg: strip foreground color. 

     ...: arguments to be passed on to 'strip.default', overriding
          whatever value it would have normally assumed 

Details:

     default strip function for trellis functions. Useful  mostly
     because of the 'style' argument - non-default styles are often
     more informative, especially when the names of the levels of the
     factor 'x' are small. Traditional use is as 'strip = function(...)
     strip.default(style=2,...)', though this can be simplified by the
     use of 'strip.custom'.

Value:

     'strip.default' is called for its side-effect, which is to draw a
     strip appropriate for multi-panel Trellis conditioning plots.
     'strip.custom' returns a function that is similar to
     'strip.default', but with different defaults for the arguments
     specified in the call.

Author(s):

     Deepayan Sarkar Deepayan.Sarkar@R-project.org

See Also:

     'xyplot', 'Lattice'

Examples:

     ## 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))

