Fisher Dennis
2013-Mar-06 17:09 UTC
[R] rainbow producing colors that do not differ sufficiently
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)
Phone: 1-866-PLessThan (1-866-753-7784)
Fax: 1-866-PLessThan (1-866-753-7784)
www.PLessThan.com
Uwe Ligges
2013-Mar-10 15:45 UTC
[R] rainbow producing colors that do not differ sufficiently
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) > Phone: 1-866-PLessThan (1-866-753-7784) > Fax: 1-866-PLessThan (1-866-753-7784) > www.PLessThan.com > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >