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 (NA s are
allowed). Note that x can be used instead of z for
convenience. |
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. |
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.
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) 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)