An example of the use of the image.scale function

image.scale_ex.R

library(devtools)
source_url('https://gist.github.com/menugget/7689145/raw/dac746aa322ca4160a5fe66c70fec16ebe26faf9/image.scale.2.r')

png("volcano_w_scale.png", width=7, height=4, units="in", res=200)
layout(matrix(c(1,2,3,0,4,0), nrow=2, ncol=3), widths=c(4,4,1), heights=c(4,1))
layout.show(4)
 
#1st image
breaks <- seq(min(volcano), max(volcano),length.out=100)
par(mar=c(1,1,1,1))
image(seq(dim(volcano)[1]), seq(dim(volcano)[2]), volcano, 
col=pal.1(length(breaks)-1), breaks=breaks-1e-8, xaxt="n", yaxt="n", ylab="", xlab="")
#Add additional graphics
levs <- pretty(range(volcano), 5)
contour(seq(dim(volcano)[1]), seq(dim(volcano)[2]), volcano, levels=levs, add=TRUE)
#Add scale
par(mar=c(3,1,1,1))
image.scale(volcano, col=pal.1(length(breaks)-1), breaks=breaks-1e-8,axis.pos=1)
abline(v=levs)
box()

 
#2nd image
breaks <- c(0,100, 150, 170, 190, 200)
par(mar=c(1,1,1,1))
image(seq(dim(volcano)[1]), seq(dim(volcano)[2]), volcano, 
col=pal.2(length(breaks)-1), breaks=breaks-1e-8, xaxt="n", yaxt="n", ylab="", xlab="")
#Add additional graphics
levs=breaks
contour(seq(dim(volcano)[1]), seq(dim(volcano)[2]), volcano, levels=levs, add=TRUE)
#Add scale
par(mar=c(1,1,1,3))
image.scale(volcano, col=pal.2(length(breaks)-1), breaks=breaks-1e-8, axis.pos=4, add.axis=FALSE)
axis(4,at=breaks, las=2)
box()
abline(h=levs)

dev.off()