tess
Create a Tessellation
Creates an object of class "tess" representing a tessellation
of a spatial region.
Usage
tess(..., xgrid = NULL, ygrid = NULL, tiles = NULL, image = NULL,
window=NULL)Arguments
- ...
- Ignored.
- xgrid,ygrid
- Cartesian coordinates of vertical and horizontal lines determining a grid of rectangles. Incompatible with other arguments.
- tiles
- List of tiles in the tessellation.
A list, each of whose elements is a window
(object of class
"owin"). Incompatible with other arguments. - image
- Pixel image which specifies the tessellation. Incompatible with other arguments.
- window
- Optional.
The spatial region which is tessellated (i.e. the union of all the tiles).
An object of class
"owin".
Details
A tessellation is a collection of disjoint spatial regions
(called tiles) that fit together to form a larger spatial
region. This command creates an object of class "tess" that
represents a tessellation.
Three types of tessellation are supported: [object Object],[object Object],[object Object]
The optional argument window specifies the spatial region
formed by the union of all the tiles. In other words it specifies the
spatial region that is divided into tiles by the tessellation.
If this argument is missing or NULL, it will be determined by
computing the set union of all the tiles. This is a time-consuming
computation. For efficiency it is advisable to specify the window.
Note that the validity of the window will not be checked.
There are methods for print, plot, [ and [<-
for tessellations. Use tiles to extract the list of
tiles in a tessellation.
Tessellations can be used to classify the points of
a point pattern, in split.ppp, cut.ppp and
by.ppp.
Value
- An object of class
"tess"representing the tessellation.
See Also
plot.tess,
[.tess,
as.tess,
tiles,
intersect.tess,
split.ppp,
cut.ppp,
by.ppp,
quadrats.
Examples
A <- tess(xgrid=0:4,ygrid=0:4)
A
B <- A[c(1, 2, 5, 7, 9)]
B
v <- as.im(function(x,y){factor(round(5 * (x^2 + y^2)))}, W=owin())
levels(v) <- letters[seq(length(levels(v)))]
E <- tess(image=v)
E