[R] color quantization / binning a variable into levels

From: David Forrest <drf5n_at_maplepark.com>
Date: Wed 22 Feb 2006 - 04:08:38 EST


Hi all,

I'd like to quantize a variable to map it into a limited set of integers for use with a colormap. "image" and filled.contour" do this mapping inside somewhere, but I'd like to choose the colors for plotting a set of polygons. Is there a pre-existing function that does something like this well? i.e., is capable of using 'breaks'?

quantize<-function(x,n=10, breaks=NULL){ # bin the variable x into n levels
  xmin<-min(x)
  xmax<-max(x)
  1+floor(n*(x-xmin)/(xmax-xmin)*.999)
}

x<- -10:10
cbind(x,quantize(x,2),quantize(x),quantize(x,21))

quantize(x,breaks=c(5,7)) #

Thanks for your time,

Dave

-- 
 Dr. David Forrest
 drf@vims.edu                                    (804)684-7900w
 drf5n@maplepark.com                             (804)642-0662h
                                   http://maplepark.com/~drf5n/

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Received on Wed Feb 22 04:24:50 2006

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