Add color scale to corresponding image plot

image.scale.2.r

#This function creates a color scale for use with the image()
#function. Input parameters should be consistent with those
#used in the corresponding image plot. The "axis.pos" argument
#defines the side of the axis. The "add.axis" argument defines
#whether the axis is added (default: TRUE)or not (FALSE).
image.scale <- function(z, zlim, col = heat.colors(12),
breaks, axis.pos=1, add.axis=TRUE, ...){
 if(!missing(breaks)){
  if(length(breaks) != (length(col)+1)){stop("must have one more break than colour")}
 }
 if(missing(breaks) & !missing(zlim)){
  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))
 }
 poly <- vector(mode="list", length(col))
 for(i in seq(poly)){
  poly[[i]] <- c(breaks[i], breaks[i+1], breaks[i+1], breaks[i])
 }
 if(axis.pos %in% c(1,3)){ylim<-c(0,1); xlim<-range(breaks)}
 if(axis.pos %in% c(2,4)){ylim<-range(breaks); xlim<-c(0,1)}
 plot(1,1,t="n",ylim=ylim, xlim=xlim, axes=FALSE, xlab="", ylab="", xaxs="i", yaxs="i", ...)  
 for(i in seq(poly)){
  if(axis.pos %in% c(1,3)){
   polygon(poly[[i]], c(0,0,1,1), col=col[i], border=NA)
  }
  if(axis.pos %in% c(2,4)){
   polygon(c(0,0,1,1), poly[[i]], col=col[i], border=NA)
  }
 }
 box()
 if(add.axis) {axis(axis.pos)}
}