nncross {spatstat}R Documentation

Nearest Neighbour in Another Point Pattern

Description

Given two point patterns X and Y, finds the nearest neighbour in Y of each point of X.

Usage

  nncross(X, Y)

Arguments

X, Y Two point patterns (objects of class "ppp").

Details

Given two point patterns X and Y this function finds, for each point of X, the the nearest point of Y. The distance between these points is also computed.

The return value is a data frame, with rows corresponding to the points of X. The first column gives the nearest neighbour distances (i.e. the ith entry is the distance from the ith point of X to the nearest point of Y). The second column gives the indices of the nearest neighbours (i.e. the ith entry is the index of the nearest point in Y.)

Note that this function is not symmetric in X and Y. To find the nearest neighbour in X of each point in Y, just use nncross(Y,X).

Value

A data frame with two columns:

dist Nearest neighbour distance
which Nearest neighbour index in Y

Author(s)

Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner rolf@math.unb.ca http://www.math.unb.ca/~rolf

Examples

  X <- runifpoint(15)
  Y <- runifpoint(20)
  N <- nncross(X,Y)$which
  # note that length(N) = 15
  plot(superimpose(X=X,Y=Y), main="nncross", cols=c("red","blue"))
  arrows(X$x, X$y, Y[N]$x, Y[N]$y, length=0.15)

[Package spatstat version 1.9-5 Index]