## S3 method for class 'im':
persp(x, \dots,
colmap=NULL, colin=x, apron=FALSE, visible=FALSE)
"im"
(see im.object
).persp.default
to control the
display.x
) containing the values that will be mapped to colours.TRUE
, a grey apron is placed
around the sides of the perspective plot.x
are visible in the perspective view. See Details.persp.default
,
together with an attribute "expand"
which gives the
relative scale of the $z$ coordinate. If argument visible=TRUE
was given, the return value
also has an attribute "visible"
which is a pixel image,
compatible with x
, with logical values which are TRUE
when the corresponding pixel is visible in the perspective view,
and FALSE
when it is obscured.
persp
method for the class "im"
. The pixel image x
must have real or integer values.
These values are treated as heights of a surface, and the
surface is displayed as a perspective plot on the current plot device,
using equal scales on the x
and y
axes.
The optional argument colmap
gives an easy way to display
different altitudes in different colours (if this is what you
want).
colmap
is a colour map (object of class"colourmap"
,
created by the functioncolourmap
)
then this colour map will be used to associate
altitudes with colours.colmap
is a character vector, then the range of
altitudes in the perspective plot will be divided intolength(colmap)
intervals, and those parts of the surface
which lie in a particular altitude range will be assigned
the corresponding colour fromcolmap
.colmap
is a function in theRlanguage
of the formfunction(n, ...)
, this function will be called
with an appropriate value ofn
to generate a character
vector ofn
colours.
Examples of such functions areheat.colors
,terrain.colors
,topo.colors
andcm.colors
.colmap
is a function in theRlanguage of the
formfunction(range, ...)
then it will be called
withrange
equal to the range of altitudes,
to determine the colour values or colour map.
Examples of such functions arebeachcolours
andbeachcolourmap
.colmap
is a list with entriesbreaks
andcol
,
thencolmap$breaks
determines the breakpoints of the altitude
intervals, andcolmap$col
provides the corresponding colours.colin
(colour input) is present,
then the colour map colmap
will be applied to
the pixel values of colin
instead of the pixel values of
x
. The result is a perspective view of a surface with
heights determined by x
and colours determined by colin
(mapped by colmap
).
If apron=TRUE
, vertical surface is drawn around the boundary
of the perspective plot, so that the terrain appears to have been
cut out of a solid material. If colour data were supplied, then
the apron is coloured light grey. Graphical parameters controlling the perspective plot
are passed through the ...
arguments
directly to the function persp.default
.
See the examples in persp.default
or in
demo(persp)
.
The vertical scale is controlled by the argument expand
:
setting expand=1
will interpret the pixel values as being in
the same units as the spatial coordinates $x$ and $y$ and
represent them at the same scale.
If visible=TRUE
, the algorithm also computes whether each pixel
in x
is visible in the perspective view. In order to be
visible, a pixel must not be obscured by another pixel which lies
in front of it (as seen from the viewing direction), and the
three-dimensional vector normal to the surface must be pointing toward the
viewer. The return value of persp.im
then has an attribute
"visible"
which is a pixel image, compatible with x
,
with pixel value equal to TRUE
if the corresponding pixel in
x
is visible, and FALSE
if it is not visible.
perspPoints
,
perspLines
for drawing additional points or lines on the surface.# an image
Z <- setcov(owin())
persp(Z, colmap=terrain.colors(128))
co <- colourmap(range=c(0,1), col=rainbow(128))
persp(Z, colmap=co, axes=FALSE, shade=0.3)
## Terrain elevation
persp(bei.extra$elev, colmap=terrain.colors(128),
apron=TRUE, theta=-30, phi=20,
zlab="Elevation", main="", ticktype="detailed",
expand=6)
Run the code above in your browser using DataCamp Workspace