[R] Log color scale

Thomas Lumley tlumley at u.washington.edu
Mon Jul 31 16:25:54 CEST 2006

On Sun, 30 Jul 2006, Uwe Ligges wrote:

> vincent at 7d4.com wrote:
>> Kartik Pappu a écrit :
>>> However I need to plot my data in a log transformed color scale.  Is
>>> this possible?  I will be happy to explain further, but basically I
>>> need to do this because there are large variations in the max and min
>>> values of my raw data and I am trying to highlight the differences in
>>> the values at the lower end of my raw data (while still displaying the
>>> values at the high end of the spectrum for comparison) so if figured
>>> the best way to represent this on a (RGB) color scale is to do it with
>>> a log transform.  I do not want to use too many colors because that
>>> make the figure too busy.
>>> Any suggestions on how to achieve this.
>> Don't use too much time to search a good palette, build it yourself.
> It is worth looking into the packages "RColorBrewer" and "colorspace".
> Some people thought about colors in graphics and wrote some code that
> might result in more appropriate colors and palettes than those that are
> quickly hacked...

colorRampPalette() will interpolate between colors (eg those from one of 
the ColorBrewer palettes) and has a bias= argument to make the colors 
closer together at one end of the scale.


Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle

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