R: Pairwise distances

pairdist.ppp {spatstat.geom} | R Documentation

## 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 pavel.grabar@issp.serpukhov.su and Adrian Baddeley Adrian.Baddeley@curtin.edu.au

### See Also

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

### Examples

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

[Package spatstat.geom version 2.3-2 Index]