D_level.colors: 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

A numeric or factor variable.

A numeric variable of breakpoints defining intervals along the range of x.

col.regions

A specification of the colors to be assigned to each interval defined by at. 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. See details below.

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.

Details

If at has length n, then it defines n-1 intervals. Values of x outside the range of at are not assigned to an interval, and the return value is NA for such values.

Colors are chosen by assigning a color to each of the n-1 intervals. If col.regions is a palette function (such as topo.colors, or the result of calling colorRampPalette), it is called with n-1 as an argument to obtain the colors. Otherwise, if there are exactly n-1 colors in col.regions, these get assigned to the intervals. If there are fewer than n-1 colors, col.regions gets recycled. If there are more, a more or less equally spaced (along the length of col.regions) subset is chosen.

Examples

Run this code

# NOT RUN {
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], ...)
       })

# }