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.