Generate a smoothly varying set of colors

colorpanel generate a set of colors that varies smoothly. redgreen, greenred, bluered, and redblue generate red-black-green, green-black-red, red-white-blue, and blue-white-red colorbars, respectively. colors

colorpanel(n, low, mid, high)
redgreen(n)
greenred(n)
bluered(n)
redblue(n)

Arguments

n

Desired number of color elements in the panel.

low, mid, high

Colors to use for the Lowest, middle, and highest values. mid may be ommited.

Details

The values for low, mid, high can be given as color names ("red"), plot color index (2), and HTML-style RGB, ("#FF0000").

If mid is supplied, then the returned color panel will consist of n - floor(n/2) HTML-style RGB elements which vary smoothly between low and mid, then between mid and high. Note that if n is even, the color mid will occur twice at the center of the sequence.

If mid is omitted, the color panel will vary smoothly beween low and high.

Value

Vector of HTML-style RGB colors.

Author

Gregory R. Warnes greg@warnes.net

See also

colors

Examples

showpanel <- function(col)
{
  image(z=matrix(1:100, ncol=1), col=col, xaxt="n", yaxt="n" )
}

par(mfrow=c(3,3))

# two colors only:
showpanel(colorpanel(8,low="red",high="green"))

# three colors
showpanel(colorpanel(8,"red","black","green"))
# note the duplicatation of black at the center, using an odd
# number of elements resolves this:
showpanel(colorpanel(9,"red","black","green"))

showpanel(greenred(64))
showpanel(redgreen(64))
showpanel(bluered(64))
showpanel(redblue(64))