| gridweights {spatstat} | R Documentation |
Computes quadrature weights for a given set of points, using the ``counting weights'' for a grid of rectangular tiles.
gridweights(X, ntile, ..., window=NULL, verbose=FALSE, npix=NULL, areas=NULL)
X |
Data defining a point pattern. |
ntile |
Number of tiles in each row and column of the rectangular grid. An integer vector of length 1 or 2. |
... |
Ignored. |
window |
Default window for the point pattern |
verbose |
Logical flag. If TRUE, information will be printed
about the computation of the grid weights.
|
npix |
Dimensions of pixel grid to use when computing a digital approximation to the tile areas. |
areas |
Vector of areas of the tiles, if they are already known. |
This function computes a set of quadrature weights
for a given pattern of points
(typically comprising both ``data'' and `dummy'' points).
See quad.object for an explanation of quadrature
weights and quadrature schemes.
The weights are computed by the ``counting weights'' rule
based on a regular grid of rectangular tiles.
First X and (optionally) window are converted into a
point pattern object. Then the bounding rectangle of the window of
the point pattern is
divided into a regular ntile[1] * ntile[2] grid of rectangular tiles.
The weight attached to a point of X is the area of the tile
in which it lies, divided by the number of points of X lying in
that tile.
For non-rectangular windows the tile areas are currently calculated
by approximating the window as a binary mask. The accuracy of this
approximation is controlled by npix, which becomes
the argument dimyx of as.mask.
Vector of nonnegative weights for each point in X.
Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner rolf@math.unb.ca http://www.math.unb.ca/~rolf
quad.object,
dirichlet.weights
Q <- quadscheme(runifpoispp(10)) X <- as.ppp(Q) # data and dummy points together w <- gridweights(X, 10) w <- gridweights(X, c(10, 10))