e2dist {AHMbook}

Calculates the pair-wise distances between two sets of points

Description

Calculates the Euclidian distance between each of the points defined by the coordinates in 'x' and each of those in 'y'.

Usage

e2dist(x, y = NULL)

Arguments

x

a 2-column matrix or data frame with the x and y coordinates of a set of points, or a length 2 vector with the coordinates of a single point.

y

an optional 2-column matrix or data frame, or a length 2 vector, with the x and y coordinates of a second set of points; if NULL, y is taken to be the same as x.

Value

A nrows(x) x nrows(y) matrix with the pair-wise distances.

Author(s)

Andy Royle

Examples

pts1 <- expand.grid(x = 1:5, y = 6:8)
pts2 <- cbind(x=runif(5, 1, 5), y=runif(5, 6, 8))
require(graphics)
plot(pts1)
points(pts2, pch=19, col='red')
e2dist(x=pts1, y=pts2)
# with a vector argument:
vec <- colMeans(pts2)
e2dist(vec, pts2)
# with y = NULL:
e2dist(x=pts2)