discpartarea: Area of Part of Disc

Description

Compute area of intersection between a disc and a window

Usage

discpartarea(X, r, W=as.owin(X))

Arguments

Point pattern (object of class "ppp") specifying the centres of the discs. Alternatively, X may be in any format acceptable to as.ppp.

Matrix, vector or numeric value specifying the radii of the discs.

Window (object of class "owin") with which the discs should be intersected.

Value

Numeric matrix, with one row for each point of X.

Details

This algorithm computes the exact area of the intersection between a window W and a disc (or each of several discs). The centres of the discs are specified by the point pattern X, and their radii are specified by r.

If r is a single numeric value, then the algorithm computes the area of intersection between W and the disc of radius r centred at each point of X, and returns a one-column matrix containing one entry for each point of X.

If r is a vector of length m, then the algorithm returns an n * m matrix in which the entry on row i, column j is the area of the intersection between W and the disc centred at X[i] with radius r[j]. If r is a matrix, it should have one row for each point in X. The algorithm returns a matrix in which the entry on row i, column j is the area of the intersection between W and the disc centred at X[i] with radius r[i,j].

Areas are computed by analytic geometry.

Examples

Run this code

data(letterR)
  X <- runifpoint(3, letterR)
  discpartarea(X, 0.2)