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. ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html