[R-sig-Geo] Specify color for "zero" raster values using levelplot

[Thiago V. dos Santos]

Hi Mel,
Thank you ver much for the suggestion. I've reproduced your palette, which looks like exactly what I was looking for. However, the grey color is still not associated to zero values in the map.
After plotting my raster with your palette as an argument:
levelplot(annual.mask, cuts=14, col.regions=myPal(15), margin=F)

I ended up with a figure like this: http://i.imgur.com/aqZkCGZ.png, where I was hoping to have all white (i.e. zero values) in the map filled with grey.
Any other ideas to achieve that?
This is the file and code to reproduce the figure:
https://dl.dropboxusercontent.com/content_link/jnv58wx0QN8ObKaiqigVckXtDmanOVYlgBxXoiym4oty5MS93xHolItNZ8tJ5gVF/file?dl=1
########################library(rasterVis)
myPal <- read.table(sep=",", text="155,29,32,Brown238,36,37,Tomato238,77,34,Tomato250,143,35,Dark.orange254,215,24,Gold214,223,47,Bitter.lemon188,218,112,Sulu179,179,179,Dark.gray124,199,177,Keppel105,202,229,Viking72,156,211,Curious.blue69,101,173,Chetwode.blue58,86,164,Governor.bay58,72,155,Dark.slate.blue44,46,118,Blue.bell")
myPal <- colorRampPalette(rgb(myPal[, 1:3], names=as.character(myPal$V4), maxColorValue=255))
r.annual <- raster("Desktop/r.annual.tif")levelplot(r.annual, cuts=14, col.regions=myPal(15), margin=F)######################## Greetings, -- Thiago V. dos Santos
PhD studentLand and Atmospheric ScienceUniversity of Minnesota 

    On Thursday, May 18, 2017 3:06 AM, Melanie Bacou <mel at mbacou.com> wrote:
 

  Simply use the same palette as in the example: library(lattice)
 
 myPal <- read.table(sep="\t", text="
 155     29     32    Brown
 238     36     37    Tomato
 238     77     34    Tomato
 250    143     35    Dark orange
 254    215     24    Gold
 214    223     47    Bitter lemon
 188    218    112    Sulu
 179    179    179    Dark gray
 124    199    177    Keppel
 105    202    229    Viking
 72     156    211    Curious blue
 69     101    173    Chetwode blue
 58     86     164    Governor bay
 58     72     155    Dark slate blue
 44     46     118    Blue bell")
 
 myPal <- colorRampPalette(rgb(myPal[, 1:3], names=as.character(myPal$V4), maxColorValue=255))
 
 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))
 levelplot(z~x*y, grid, cuts=14, col.regions=myPal(15), margin=FALSE)
 
 --Mel.
 
 On 05/17/2017 01:25 PM, Thiago V. dos Santos via R-sig-Geo wrote:
  
 Dear all,

I am trying to change the color for zero values in a map produced using levelplot to plot a raster file. Specifically, I want to reproduce this figure: http://i.imgur.com/mjXxZhO.png, where a red to blue scale is used, but notice that zero values have been replaced by grey.

As an example, let's use an adapted version of the August irradiation code from the rasterVis webpage:

################################
library(raster)
library(ncdf4)
library(rasterVis)

##Solar irradiation data from CMSAF 
old <- setwd(tempdir())
download.file('https://raw.github.com/oscarperpinan/spacetime-vis/master/data/SISmm2008_CMSAF.zip',
'SISmm2008_CMSAF.zip', method='wget')
unzip('SISmm2008_CMSAF.zip')

listFich <- dir(pattern='\\.nc')
stackSIS <- stack(listFich)
stackSIS <- stackSIS * 24 ##from irradiance (W/m2) to irradiation Wh/m2
idx <- seq(as.Date('2008-01-15'), as.Date('2008-12-15'), 'month')

SISmm <- setZ(stackSIS, idx)
names(SISmm) <- month.abb

setwd(old)

# Set color palette
myTheme=rasterTheme(region=brewer.pal('RdBu', n=11))

Aug <- raster(SISmm, 8)
meanAug <- cellStats(Aug, mean)
levelplot(Aug - meanAug, par.settings = myTheme, margin=FALSE)

################################

In the example above, how can I replace the color of "zero values" with grey?

Thanks,
 -- Thiago V. dos Santos

PhD student
Land and Atmospheric Science
University of Minnesota

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