[R] rainbow producing colors that do not differ sufficiently

[Uwe Ligges]

See the CRAN task view on Graphics and its section on colors:
http://cran.r-project.org/web/views/Graphics.html

Uwe Ligges


On 06.03.2013 18:09, Fisher Dennis wrote:
> R 2.15.2
> OS X
>
> Colleagues,
>
> I often use rainbow to select colors.  I encountered a surprise with rainbow(11).   It yielded three greens (in positions 4-6).  The first two of these are quite similar.  The man pages suggest that this might be the case:
> 	equispaced hues in RGB space tend to cluster at the red, green and blue primaries
>
> The following code illustrates the problem -- the colors labeled 4 and 5 are quite similar.
> 	plot(1, type="n", xlim=c(1, 10), ylim=c(0, 1), axes=F, xlab="", ylab="")
> 	for (which in 3:7)	
> 		{
> 		rect(which - 1, 0, which, 1, border=NA, col=rainbow(11)[which])
> 		text(which - 0.5, 0.8, which)
> 		text(which - 0.5, 0.2, rainbow(11)[which], srt=90)
> 		}
>
> In this case, I overcame the problem by replacing one element on the rainbow vector with a different green.
>
> Is there some better approach to this by which I could automate the entire process but prevent this similarity of colors?
>
> Dennis
>
> Dennis Fisher MD
> P < (The "P Less Than" Company)
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