pairdist.default

Pairwise distances

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", squared=FALSE)

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. 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.

See Also

crossdist, nndist, Kest

Aliases

• pairdist.default

Examples

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