pairdist.ppp {spatstat.geom}

Pairwise distances

Description

Computes the matrix of distances between all pairs of points in a point pattern.

Usage

  ## S3 method for class 'ppp'
pairdist(X, ...,
                        periodic=FALSE, method="C", squared=FALSE, metric=NULL)

Arguments

X

A point pattern (object of class "ppp").

...

Ignored.

periodic

Logical. Specifies whether to apply a periodic edge correction.

method

String specifying which method of calculation to use. Values are "C" and "interpreted". Usually not specified.

squared

Logical. If squared=TRUE, the squared distances are returned instead (this computation is faster).

metric

Optional. A metric (object of class "metric") that will be used to define and compute the distances.

Details

This is a method for the generic function pairdist.

Given a point pattern X (an object of class "ppp"), this function computes the Euclidean distances between all pairs of points in X, and returns the matrix of distances.

Alternatively if periodic=TRUE and the window containing X is a rectangle, then the distances will be computed in the ‘periodic’ sense (also known as ‘torus’ distance): opposite edges of the rectangle are regarded as equivalent. This is meaningless if the window is not a rectangle.

If squared=TRUE then the squared Euclidean distances d^2 are returned, instead of the Euclidean distances d. The squared distances are faster to calculate, and are sufficient for many purposes (such as finding the nearest neighbour of a point).

The argument method is not normally used. It is retained only for checking the validity of the software. If method = "interpreted" then the distances are computed using interpreted R code only. If method="C" (the default) then C code is used. The C code is somewhat faster.

Value

A square matrix whose [i,j] entry is the distance between the points numbered i and j.

Author(s)

Pavel Grabarnik [e-mail] and Adrian Baddeley [e-mail].

See Also

pairdist, pairdist.default, pairdist.psp, crossdist, nndist, Kest

Examples

   d <- pairdist(cells)
   d <- pairdist(cells, periodic=TRUE)
   d <- pairdist(cells, squared=TRUE)