R: A function to compute false colors representing a numeric or...

D_level.colors {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 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.

### 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.

### 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`, `colorRampPalette`.

### 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], ...)
           })

[Package lattice version 0.20-29 Index]