level.colors             package:lattice             R Documentation

A function to compute false colors representing a numeric or
categorical variable

Description:

     Calculates false colors from a numeric variable (including
     factors, using their numeric codes) given a color scheme and
     breakpoints.

Usage:

     level.colors(x, at, col.regions, colors = TRUE, ...)

Arguments:

       x: A numeric or 'factor' variable 

      at: A numeric variable of breakpoints where colors change 

col.regions: A specification of the colors to be used.  This could be
          either a vector of colors, or a function that produces a
          vector of colors when called with a single argument giving
          the number of colors. 

  colors: logical indicating whether colors should be computed and
          returned.  If 'FALSE', only the indices representing which
          interval (among those defined by 'at') each value in 'x'
          falls into is returned.  

     ...: Extra arguments, ignored. 

Value:

     A vector of the same length as 'x'.  Depending on the 'colors'
     argument, this could be either a vector of colors (in a form
     usable by R), or a vector of integer indices representing which
     interval the values of 'x' fall in.

Author(s):

     Deepayan Sarkar deepayan.sarkar@r-project.org

See Also:

     'levelplot'

Examples:

     depth.col <-
         with(quakes, 
              level.colors(depth, at = do.breaks(range(depth), 30),
                           col.regions = terrain.colors))

     xyplot(lat ~ long | equal.count(stations), quakes,
            strip = strip.custom(var.name = "Stations"),
            colours = depth.col,
            panel = function(x, y, colours, subscripts, ...) {
                panel.xyplot(x, y, pch = 21, col = "transparent",
                             fill = colours[subscripts], ...)
            })

