Plot a rasterVis::levelplot with a colour ramp diverging around zero

diverge0.R

diverge0 <- function(p, ramp) {
  # p: a trellis object resulting from rasterVis::levelplot
  # ramp: the name of an RColorBrewer palette (as character), a character 
  #       vector of colour names to interpolate, or a colorRampPalette.
  require(RColorBrewer)
  require(rasterVis)
  if(length(ramp)==1 && is.character(ramp) && ramp %in% 
     row.names(brewer.pal.info)) {
    ramp <- suppressWarnings(colorRampPalette(brewer.pal(11, ramp)))
  } else if(length(ramp) > 1 && is.character(ramp) && all(ramp %in% colors())) {
    ramp <- colorRampPalette(ramp)
  } else if(!is.function(ramp)) 
    stop('ramp should be either the name of a RColorBrewer palette, ', 
         'a vector of colours to be interpolated, or a colorRampPalette.')
  rng <- range(p$legend[[1]]$args$key$at)
  s <- seq(-max(abs(rng)), max(abs(rng)), len=1001)
  i <- findInterval(rng[which.min(abs(rng))], s)
  zlim <- switch(which.min(abs(rng)), `1`=i:(1000+1), `2`=1:(i+1))
  p$legend[[1]]$args$key$at <- s[zlim]
  p[[grep('^legend', names(p))]][[1]]$args$key$col <- ramp(1000)[zlim[-length(zlim)]]
  p$panel.args.common$col.regions <- ramp(1000)[zlim[-length(zlim)]]
  p
}

Example

library(rasterVis)
r <- raster(matrix(runif(100, -10, 30), 10))
p <- levelplot(r, margin=FALSE, at=seq(-10, 30, 1))
diverge0(p, 'RdBu')

How can I revert the ramp from brewer.pal in the function?
For example:
rev(colorRampPalette(brewer.pal(11, "RdBu"))

@FVFaleiro you can pass a colorRampPalette to the function, so just move the rev inside the colorRampPalette:

diverge0(p, colorRampPalette(rev(brewer.pal(11, "RdBu"))))

Note that the tmap package has some useful functionality for this as well:

library(tmap)
tm_shape(r) +
  tm_raster(midpoint=0, style='cont', title='foo', palette='-RdBu',
            breaks=pretty(cellStats(r, range), 7), legend.reverse=TRUE) +
  tm_layout(legend.outside=TRUE)

Great, @johnbaums! Thanks!
How do you set the legend in the rasterVis to be in a continuous aspect? Aparently the default of levelplot have the colors like categories instead a smoth transition between the colors.

@FVFaleiro you just need to set enough breaks along the legend:

r <- raster::raster(matrix(runif(100), 10))
rasterVis::levelplot(r, at=seq(0, 1, length.out=100))

Thanks, @johnbaums!

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