I've gotten good results using the sine function to map colors.
For example, when plotting x, map the range(x) to (-pi/2,pi/2)
which the sine will transform to (-1,1), then add 1 and multiply by
half the desired number of colors. Now the integer values will
pick the colors and give a pleasing display.
If the "squeeze" is taking place only over one of the tails (which
sounds like your case) map the range from (0,pi/2) or (-pi/2,0) and
make the necessary scaling adjustments to cover the number of
colors desired.
Essentially, you are transforming the color mapping instead of
transforming your data.
Clint
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On Thu, 20 Jan 2011, Jim Lemon wrote:
On 01/20/2011 09:19 AM, claudia tebaldi wrote:
Hi all
I'm plotting colored contour maps using filled.contour. My levels
are very unevenly spaced, with, say, high resolution in the small
numbers but ranges that can be an order of magnitude or two larger in
absolute value compared to where the action takes place. Aside from
transforming the data, is there a way to control the color spacing in
the key to the right of the map? Right now I get most of the key
length taken up by a couple of colors and the rest all squeezed into
thin slices, which also creates a problem with the fourth axis labels
getting drawn on top of one another.
Hi Claudia,
You can roll your own color key with the color.legend function in plotrix.
Just specify the colors you want in "rect.col" and the labels in "legend".
Jim
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