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
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=red), and HTML-style RGB,
("#FF0000"=red).
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.
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))