pairdist.default: Pairwise distances

Description

Computes the matrix of distances between all pairs of points in a set of points

Usage

## S3 method for class 'default':
pairdist(X, Y=NULL, \dots, period=NULL, method="C")

Arguments

X,Y

Arguments specifying the coordinates of a set of points. Typically X and Y would be numeric vectors of equal length. Alternatively Y may be omitted and X may be a list with two components

...

Ignored.

period

Optional. Dimensions for periodic edge correction.

method

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

Value

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

Details

Given the coordinates of a set of points, this function computes the Euclidean distances between all pairs of points, and returns the matrix of distances. It is a method for the generic function pairdist.

The arguments X and Y must determine the coordinates of a set of points. Typically X and Y would be numeric vectors of equal length. Alternatively Y may be omitted and X may be a list with two components named x and y, or a matrix or data frame with two columns. Alternatively if period is given, then the distances will be computed in the `periodic' sense (also known as `torus' distance). The points will be treated as if they are in a rectangle of width period[1] and height period[2]. Opposite edges of the rectangle are regarded as equivalent. 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.

Examples

Run this code

x <- runif(100)
   y <- runif(100)
   d <- pairdist(x, y)
   d <- pairdist(cbind(x,y))
   d <- pairdist(x, y, period=c(1,1))

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