imageScale: Make a color scale to accompany an image or other plot

In satin: Visualisation and Analysis of Ocean Data Derived from Satellites

Make a color scale to accompany an image or other plot

Description

The imageScale function is wrapper for imageScale and accepts the same arguments. It 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. All arguments are similar to those in the image function. Appearance is best when incorporated with layout.

Usage

imageScale(z, zlim, col = heat.colors(12), breaks, axis.pos = 1,
  add.axis = TRUE, xlim = NULL, ylim = NULL, log, ...)

Arguments

z	A vector or matrix of values.
zlim	Limits of the color scale values.
col	Vector of color values (default is 12 colors from the heat.colors palette).
breaks	Break points for color changes. If breaks is specified then zlim is unused and the algorithm used follows cut, so intervals are closed on the right and open on the left except for the lowest interval which is closed at both ends.
axis.pos	Position of the axis (1=bottom, 2=left, 3=top, 4=right) (default = 1).
add.axis	Logical (TRUE/FALSE). Defines whether the axis is added (default: TRUE).
xlim	Limits for the x-axis.
ylim	Limits for the y-axis.
log	logical. If TRUE, z is log transformed (base 10).
...	Additional graphical parameters to pass to the image function.

Author(s)

Marc Taylor, modified for log scale by Héctor Villalobos

Examples

# Make color palettes
pal.1=colorRampPalette(c("green4", "orange", "red", "white"), space="rgb", bias=0.5)
pal.2=colorRampPalette(c("blue", "cyan", "yellow", "red", "pink"), space="rgb")

# Make images with corresponding scales
op <- par(no.readonly = TRUE)
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(3,1,0,1))
imageScale(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(1,0,1,3))
imageScale(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)
par(op)

satin documentation built on Sept. 23, 2022, 1:06 a.m.