[R] specify breaks in divergent palette in RColorBrewer: was divergent colors around zero in levelplot()
Don McKenzie
dmck at u.washington.edu
Tue Nov 26 01:27:18 CET 2013
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$z <- cos(r^2) * exp(-r/(pi^3))
# now use RColorBrewer to get a palette
library("RColorBrewer”)
levelplot(z~x*y, grid,col.regions=brewer.pal(6,"BrBG”)) # the numeric argument to brewer.pal is the number of colors used — I tried several
This gives me a nice brown-to-green gradient but does not (AFAICS) give me control over where the center of the divergence lies. Even in this symmetrical
example, I can’t get it to be at zero — it repeats on either side of zero.
thanks to anyone who pages through all this and makes a suggestion, even if it doesn’t work. :-)
On Nov 22, 2013, at 10:25 PM, Bert Gunter <gunter.berton at gene.com> wrote:
> Use the Rcolorbrewer package.
>
> -- Bert
>
> On Fri, Nov 22, 2013 at 8:43 PM, Don McKenzie <dmck at u.washington.edu> wrote:
>> I would like to produce a levelplot with divergent colors such that increasingly negative values of Z get darker in the first color and increasingly
>> positive values get darker in the second color. this is common in cartography. I have tried tinkering with the col.regions argument but the best I can do
>> is to get the split in the middle of my range of Z, but in my particular case range(Z) is (-1,12).
>>
>> I am using R 3.0.2 on OSX 10.9
>>
>> Here is an example
>>
>> x <- y <- c(1:25)
>> grid <- expand.grid(x=x,y=y)
>> grid$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
dmck at uw.edu
More information about the R-help
mailing list