[Rd] new function: showcolors {base}

[Martin Maechler]

>>>>> "Wolfram" == Wolfram Fischer <- Z/I/M <wolfram@fischer-zim.ch>>
>>>>>     on Fri, 24 Jan 2003 10:22:09 +0100 writes:

    Wolfram> I propose to add a function that allows
    Wolfram> to display colors selected by a text pattern
    Wolfram> or by color vectors in a plot.

    Wolfram> Wolfram Fischer

    Wolfram> #--- showcolors.R

I had a much simpler idea
added to  example(palettes) for R-devel (aka "pre-1.7.0") about
2 weeks ago:

Maybe one could combine some of the underlying ideas...
---
Martin Maechler <maechler@stat.math.ethz.ch>	http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum  LEO C16	Leonhardstr. 27
ETH (Federal Inst. Technology)	8092 Zurich	SWITZERLAND
phone: x-41-1-632-3408		fax: ...-1228			<><


 ##------ Some palettes ------------
 demo.pal <-
   function(n, border = if (n<32) "light gray" else NA,
	    main = paste("color palettes;  n=",n),
	    ch.col = c("rainbow(n, start=.7, end=.1)", "heat.colors(n)",
		       "terrain.colors(n)", "topo.colors(n)", "cm.colors(n)"))
 {
     nt <- length(ch.col)
     i <- 1:n; j <- n / nt; d <- j/6; dy <- 2*d
     plot(i,i+d, type="n", yaxt="n", ylab="", main=main)
     for (k in 1:nt) {
	 rect(i-.5, (k-1)*j+ dy, i+.4, k*j,
	      col = eval(parse(text=ch.col[k])), border = border)
	 text(2*j,  k * j +dy/4, ch.col[k])
     }
 }
 n <- if(.Device == "postscript") 64 else 16
      # Since for screen, larger n may give color allocation problem
 demo.pal(n)

    Wolfram> showcolors <-  function(

    ......