color.gradient {plotrix}R Documentation

Calculate an arbitrary sequence of colors.

Description

color.gradient calculates sequences of colors by linearly interpolating between the values specified for each color. If the length of a vector of colors is the same as nslices it is not changed. If any length is greater than nslices, it is truncated to that length. If any color values are less than 0 or greater than 1, they are rescaled to that range.

Usage

 color.gradient(reds,greens,blues,nslices=50)

Arguments

reds,greens,blues vectors of the values of the color components as 0 to 1.
nslices The number of color "slices".

Value

A vector of hexadecimal color values as used by col.

Note

The function is mainly useful for defining a set of colors to represent a known number of gradations. Such a set can be used to assign a grade to a small number of values (e.g. points on a scatterplot - but see color.scale for large numbers) and display a color bar using gradient.rect as a legend.

Author(s)

Jim Lemon

See Also

rescale,approx,color.scale

Examples

 # try it with red endpoints, green midpoints, and a blue vector longer
 # than 'nslices'
 color.gradient(c(0,1),c(1,0.6,0.4,0.3,0),seq(0.1,0.6,length=60))

[Package plotrix version 2.1-5 Index]