image {base}

R Documentation

Display a color image

Description

Creates a grid of colored or gray-scale rectangles with colors corresponding to the values in z. This can be used to display three-dimensional or spatial data aka “images”. The functions heat.colors, terrain.colors and topo.colors create heat-spectrum (red to white) and topographical color schemes suitable for displaying ordered data, with n giving the number of colors desired.

Usage

image(x, y, z, zlim, col = heat.colors(12),
      add = FALSE, xaxs = "i", yaxs = "i", xlab, ylab, ...)

Arguments

x, y	locations of grid lines at which the values in z are measured. These must be in ascending order. By default, equally spaced values from 0 to 1 are used.
z	a matrix containing the values to be plotted (NAs are allowed).
zlim	the minimum and maximum z values for which colors will be plotted. Each of the given colors will be used to color an equispaced interval of this range.
col	a list of colors such as that generated by rainbow, heat.colors, topo.colors, terrain.colors or similar functions.
add	logical; if TRUE, add to current plot (and disregard the following arguments). This is rarely useful because image “paints” over existing graphics.
xaxs, yaxs	style of x and y axis. The default "i" is appropriate for images. See par.
xlab, ylab	each a character string giving the labels for the x and y axis. Default to the ‘call names’ of x or y, or to "" if these where unspecified.
...	graphical parameters for plot may also be passed as arguments to this function.

Note

Based on a function by Thomas Lumley thomas@biostat.washington.edu.

See Also

contour, heat.colors, topo.colors, terrain.colors, rainbow, hsv, par.

Examples

x <- y <- seq(-4*pi, 4*pi, len=27)
r <- sqrt(outer(x^2, y^2, "+"))
image(z = z <- cos(r^2)*exp(-r/6), col=gray((0:32)/32))
image(z=z, axes=F,
      main="Math can be beautiful ...", xlab=expression(cos(r^2) * e^{-r/6}))
contour(z=z, add=T)

data(volcano)
x <- 10*(1:nrow(volcano))
y <- 10*(1:ncol(volcano))
image(x, y, volcano, col = terrain.colors(100), axes = FALSE)
contour(x, y, volcano, levels = seq(90, 200, by=5), add = TRUE, col = "peru")
axis(1, at = seq(100, 800, by = 100))
axis(2, at = seq(100, 600, by = 100))
box()
title(main = "Maunga Whau Volcano", font.main = 4)

---