[R] Colours for 3-way probabilities

Carl Witthoft carl at witthoft.com
Sat Dec 18 17:44:22 CET 2010

There are a couple Venn Diagram functions out there.

But I would strongly recommend against making charts like this.  There 
are too many colors, and even non-colorblind people will find them to be 
a pain to discriminate, let alone remember what the coding means.

Assuming you want to show the distribution on a cartographic map,  maybe 
a mini-barchart in each state or county would be better, or three 
non-overlapping 'bubbles' whose diameter or area maps to votecount.

Tufte has written a bunch about this sort of problem.

Are there any R functions for creating palettes for three-way data? For 
example, election maps for three parties where pure red, blue, and green 
show 100% for the Red, Blue, and Green parties respectively, magenta 
shows a 50-50 Red-Blue split with 0 for the Greens, cyan a 50-50 
Blue/Green split with no Red votes and so on, with grey, black or white 
at a 1/3,1/3,1/3 split vote.

I've spent a couple of half hours knocking out a function to do various 
versions of that, including using Red/Yellow/Blue for the primaries with 
Orange/Green/Purple for the 50/50s. I'm wondering if

    1. There's existing functionality in one of the packages on CRAN 
(I've had a look and googled)
    2. Anyone can point me to information about colour perception of 
this kind of three-way colour scheme.

Thanks muchly.

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