[BioC] heatmap colours

[Johannes Hüsing]

Jean Yee Hwa Yang <jean at biostat.ucsf.edu> [Mon, May 12, 2003 at 07:31:59PM CEST]:
[...]
> 
> ## Red -- Black -- Green
[...]
> ## Red -- white -- Green
[...]
> ## blue--yellow
[...]

General discussion about the usefulness of heat maps aside, why is 
everyone infatuated with the red/green contrast? Just because cDNA
chips are marked with red and green dye? We are not looking at a
chip image here, so generally we are free wrt choice of colours.

Red and green is less than optimal for several reasons:

- A non-neglectable proportion of the population, especially the
  male sector of it, cannot distinguish between those colours.
- It makes for poor contrast when transformed to grayscale.

The visualization guides I have read don't condone a red/green
contrast scale (while Edward Tufte doesn't specifically list it as a
deterring example, he doesn't recommend it either).  One suggestion is
a palet along black -- red -- orange -- yellow -- white, mimicking the
appearance of a black body heated up.  (That would cause "heat map" to
be an apt term at last.

ok. I'm feeling better now.


Johannes
-- 
Johannes Hüsing   There is something fascinating about science. One gets
hannes at ruhrau.de  such wholesale returns of conjecture from such a 
                  trifling investment of fact.                Mark Twain