Convert values to color levels

val2col.3.0.r

#this function converts a vector of values("z") to a vector of color
#levels. One must define the number of colors. The limits of the color
#scale("zlim") or the break points for the color changes("breaks") can 
#also be defined. when breaks and zlim are defined, breaks overrides zlim.
val2col<-function(z, zlim, col = heat.colors(12), breaks){
 if(!missing(breaks)){
  if(length(breaks) != (length(col)+1)){stop("must have one more break than colour")}
 }
 if(missing(breaks) & !missing(zlim)){
  zlim[2] <- zlim[2]+c(zlim[2]-zlim[1])*(1E-3)#adds a bit to the range in both directions
  zlim[1] <- zlim[1]-c(zlim[2]-zlim[1])*(1E-3)
  breaks <- seq(zlim[1], zlim[2], length.out=(length(col)+1)) 
 }
 if(missing(breaks) & missing(zlim)){
  zlim <- range(z, na.rm=TRUE)
  zlim[2] <- zlim[2]+c(zlim[2]-zlim[1])*(1E-3)#adds a bit to the range in both directions
  zlim[1] <- zlim[1]-c(zlim[2]-zlim[1])*(1E-3)
  breaks <- seq(zlim[1], zlim[2], length.out=(length(col)+1))
 }
 CUT <- cut(z, breaks=breaks)
 colorlevels <- col[match(CUT, levels(CUT))] # assign colors to heights for each point
 return(colorlevels)
}