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have a look at http://colorbrewer.org/
and install the package RColorBrewer
David
On Jan 7, 2006, at 20:34, bogdan romocea wrote:
> Dear useRs,
>
> I got stuck trying to generate a palette of topographic colors that
> would satisfy these two requirements:
> - the pallete must be 'anchored' at 0 (just like on a map), with
> light blue/lawn green corresponding to data values close to 0 (dark
> blue to light blue for negative values, green-yellow-brown for
> positive values)
> - the brown must get darker for higher positive values.
>
> topo.colors() fails both requirements and AFAICS lacks any options to
> control its behavior.
> #---unsatisfactory topo.colors() behavior
> topoclr <- function(tgt)
> {
> clr <- topo.colors(length(tgt))
> clr <- clr[round(rank(tgt),0)]
> plot(tgt,pch=15,col=clr)
> }
> par(mfrow=c(2,1)) ; topoclr(-50:50) ; topoclr(-20:80)
>
> An acceptable solution would be something like this
> grayclr <- function(tgt)
> {
> tgt <- sort(tgt) ; neg <- which(tgt < 0)
> clrneg <- gray(0:length(tgt[neg])/length(tgt[neg]))
> clrpos <- gray(length(tgt[-neg]):0/length(tgt[-neg]))
> clr <- c(clrneg,clrpos)
> plot(tgt,pch=15,col=clr)
> }
> par(mfrow=c(2,1)) ; grayclr(-50:50) ; grayclr(-20:80)
> if only I could make gray() use blue/brown instead of black (I tried a
> couple of things but got stuck again).
>
> Any suggestions?
>
> Thank you,
> b.
>
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