[R-sig-Geo] ramping four color in xy space

[Tomislav Hengl]

Dear Holger,

This is a small script that uses [colorspace] library to run calculations with colors (some methods
are limited to 256 colors only):

http://spatial-analyst.net/scripts/whitening.R

If you assign R,G,B values spatially and then interpolate them (they have to be in the 0-1 range),
then it is relatively easy to produce an RGB image.

cheers,

Tom Hengl
http://spatial-analyst.net/wiki/index.php?title=Uncertainty_visualization 


PS: maybe you should also consider color mixing:

Hengl T., Walvoort D.J.J., Brown A. 2004. A double continuous approach to visualisation and analysis
of categorical maps. Int. Jou. of Geographical Information Science, 18(2): 183-202.
http://dx.doi.org/10.1080/13658810310001620924 


-----Original Message-----
From: r-sig-geo-bounces at stat.math.ethz.ch [mailto:r-sig-geo-bounces at stat.math.ethz.ch] On Behalf Of
Holger Kreft
Sent: Tuesday, November 18, 2008 9:38 AM
To: R-sig-Geo at stat.math.ethz.ch
Subject: [R-sig-Geo] ramping four color in xy space

Hi,

I have run a metaMDS(vegan) on ecological community data and have a nice 
plot in xy space.
What I want to do next is to assign a unique color to each point in the 
plot and then look at how these communities map out in geographic space.
So, each corner of the plot has a color (let's say green, blue, red and 
yellow). I guess I have to ramp the colors for the space inbetween.
The right plot here illustrate how the palette should look like: 
http://www.flickr.com/photos/erniebooth/183647844/

Does anyone have experience in ramping four colours in 2-D? I looked at 
a lot of packages, but they are all not doing what I want.

Any hint / help is greatly appreciated!

Thanks,

Holger

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