Extract.tess: Extract or Replace Subset of Tessellation
Description
Extract, change or delete a subset of the tiles of a tessellation,
to make a new tessellation.
Usage
## S3 method for class 'tess':
[(x, ...)
## S3 method for class 'tess':
[(x, ...) <- value
Arguments
x
A tessellation (object of class "tess").
...
One argument that specifies the subset to be extracted or changed.
Any valid format for the subset index in a list.
value
Replacement value for the selected tiles of the tessellation.
A list of windows (objects of class "owin") or NULL.
Value
A tessellation (object of class "tess").
Details
A tessellation (object of class "tess", see tess)
is effectively a list of tiles (spatial regions) that cover a spatial region.
The subset operator [.tess extracts some
of these tiles and forms a new tessellation, which of course covers a
smaller region than the original.
The replacement operator changes the selected tiles. The replacement
value may be either NULL (which causes the selected tiles
to be removed from x) or a list of the same length as
the selected subset. The entries of value may be windows
(objects of class "owin") or NULL to indicate that the
corresponding tile should be deleted.
Generally it does not make sense to replace a tile in a tessellation
with a completely different tile, because the tiles are expected to
fit together. However this facility is sometimes useful for making
small adjustments to polygonal tiles.