smacpod (version 1.3.0)

nn: Determine nearest neighbors

Description

nn determines the nearest neighbors for a set of observations.

Usage

nn(d, k, method = "c", self = FALSE)

Arguments

d

A square distance matrix for the set of coordinates of interest.

k

The number of numbers to return (if method = "c") or the distance for which observations are considered neighbors (if method = "d").

method

The method of determining the neighbors. The default is "c", specifying that the k nearest neighbors (the count of neighbors) for each observation should be returned. The alternative is "d", meaning that neighbors

self

A logical indicating whether an observation is a neighbor with itself. The default is FALSE.

Value

• Returns the indexes of the nearest neighbors as a matrix if method = "c" and a list otherwise. For each row or element of the list, the indexes are ordered from nearest to farthest.

Details

This function can determine nearest neighbors in two ways: 1. by total count or 2. by distance. If method = "c", then k determines the total number of neighbors to return for each observation. If method = "d", then k determines the distance for which an observation is considered a neighbor.

Examples

data(grave)
# make distance matrix
d = as.matrix(dist(cbind(grave$x, grave$y)))
# 3 nearest neighbors
nnc = nn(d, k = 3, method = "c")
# nearest neighbors within k units of each observation
nnd = nn(d, k = 200, method = "d")