Bert or anyone else familiar with RColorBrewer:

Has anyone tried to accomplish with RColorBrewer what I asked about in my 
original post (below)? 

Here is an example cribbed from the levelplot() help examples

x <- seq(pi/4, 5 * pi, length.out = 100)
y <- seq(pi/4, 5 * pi, length.out = 100)
r <- as.vector(sqrt(outer(x^2, y^2, "+")))
grid <- expand.grid(x=x, y=y)
grid$z <- cos(r^2) * exp(-r/(pi^3))

# now use RColorBrewer to get a palette

library("RColorBrewer”)
levelplot(z~x*y, grid,col.regions=brewer.pal(6,"BrBG”))   # the numeric 
argument to brewer.pal is the number of colors used — I tried several

This gives me a nice brown-to-green gradient but does not (AFAICS) give me 
control over where the center of the divergence lies. Even in this symmetrical
example, I can’t get it to be at zero — it repeats on either side of zero.

thanks to anyone who pages through all this and makes a suggestion, even if it 
doesn’t work.  :-)

On Nov 22, 2013, at 10:25 PM, Bert Gunter <gunter.ber...@gene.com> wrote:

> Use the Rcolorbrewer package.
> 
> -- Bert
> 
> On Fri, Nov 22, 2013 at 8:43 PM, Don McKenzie <d...@u.washington.edu> wrote:
>> I would like to produce a levelplot with divergent colors such that 
>> increasingly negative values of Z get darker in the first color and 
>> increasingly
>> positive values get darker in the second color.  this is common in 
>> cartography. I have tried tinkering with the col.regions argument but the 
>> best I can do
>> is to get the split in the middle of my range of Z, but in my particular 
>> case range(Z) is (-1,12).
>> 
>> I am using R 3.0.2 on OSX 10.9
>> 
>> Here is an example
>> 
>> x <- y <- c(1:25)
>> grid <- expand.grid(x=x,y=y)
>> grid$z <- sort(runif(625,min=-1,max=12))
>> levelplot(z ~ x*y,grid)   # produces the default pink and blue but the split 
>> is at ~5.5
>> 
>> # do something clever here
>> # e.g., my.colors <- <create a palette that splits at zero>
>> 
>> levelplot(z ~ x*y,grid,col.regions=my.colors)  # so there should be some 
>> light pink at the bottom and the rest increasingly intense blue
>> 
>> Ideas appreciated.  Thanks in advance.
>> 
>> 
> 
> Bert Gunter
> Genentech Nonclinical Biostatistics
> 
> (650) 467-7374

Don McKenzie
Research Ecologist
Pacific Wildland Fire Science Lab
US Forest Service

Affiliate Professor
School of Environmental and Forest Sciences
University of Washington
d...@uw.edu

______________________________________________
R-help@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.

Reply via email to