spatstat (version 1.3-2)

gridweights: Compute Quadrature Weights Based on Grid Counts

Description

Computes quadrature weights for a given set of points, using the ``counting weights'' for a grid of rectangular tiles.

Usage

gridweights(X, nx, ny, window=NULL)

Arguments

X

Data defining a point pattern.

nx

Number of tiles in each row of the rectangular grid.

ny

Number of tiles in each column of the rectangular grid.

window

Default window for the point pattern

Value

• Vector of nonnegative weights for each point in X.

Details

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 $nx \times ny$ 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.

See Also

quad.object, dirichlet.weights

Examples

library(spatstat)
  Q <- quadscheme(runifpoispp(10))
  X <- as.ppp(Q) # data and dummy points together
  w <- gridweights(X, 10, 10)