| image {base} | R Documentation |
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.
image(x, y, z, zlim, col = heat.colors(12),
add = FALSE, xaxs = "i", yaxs = "i", xlab, ylab, ...)
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. If x is a list,
its components x$x and x$y are used for x
and y, respectively. If the list has component z this
is used for z. |
z |
a matrix containing the values to be plotted (NAs are
allowed). Note that x can be used instead of z for
convenience. |
zlim |
the minimum and maximum z values for which colors
should be plotted. Each of the given colors will be used to color an
equispaced interval of this range. The midpoints of the
intervals cover the range, so that values just outside the range
will be plotted. |
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. |
The length of x should be equal to the nrow(x)+1 or
nrow(x). In the first case x specifies the boundaries
between the cells: in the second case x specifies the
midpoints of the cells. Similar reasoning applies to y. It
probably only makes sense to specify the midpoints of an
equally-spaced grid. If you specify just one row or column and a
length-one x or y, the whole user area in the
corresponding direction is filled.
Based on a function by Thomas Lumley thomas@biostat.washington.edu.
The way in which zlim is divided into colours will be changed
for the next major release (1.1.0) to divide the range into
equal-length intervals.
contour,
heat.colors, topo.colors,
terrain.colors, rainbow,
hsv, par.
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, axes=F, main="Math can be beautiful ...",
xlab=expression(cos(r^2) * e^{-r/6}))
contour(z, add=T, drawlabels=F)
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)