tess {spatstat} | R Documentation |
Creates an object of class "tess"
representing a tessellation
of a spatial region.
tess(..., xgrid = NULL, ygrid = NULL, tiles = NULL, image = NULL, window=NULL)
... |
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" .
|
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:
x
and
y
axes. They may or may not have equal size and shape.
The arguments xgrid
and ygrid
determine
the positions of the vertical and horizontal grid lines,
respectively. (See quadrats
for another way to do this.)
tiles
is a list of these tiles,
which are objects of class "owin"
.
image
is a pixel image (object of class
"im"
) with factor values. Each level of the factor
represents a different tile of the tessellation. The pixels that
have a particular value of the factor constitute a tile.
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
.
An object of class "tess"
representing the tessellation.
Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner r.turner@auckland.ac.nz
plot.tess
,
[.tess
,
as.tess
,
tiles
,
intersect.tess
,
split.ppp
,
cut.ppp
,
by.ppp
,
quadrats
.
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