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Display a color image
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 (NA s 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.
|
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.
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)