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Plot a rasterVis::levelplot with a colour ramp diverging around zero
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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$par.settings$regions$col <- ramp(1000)[zlim[-length(zlim)]] | |
p | |
} |
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