funs.kNNdist: Functions for the k^{th} and 'k' NN distances

In nnspat: Nearest Neighbor Methods for Spatial Patterns

Functions for the k^{th} and k NN distances

Description

Two functions: kthNNdist and kNNdist.

kthNNdist returns the distances between subjects and their k^{th} NNs. The output is an n \times 2 matrix where n is the data size and first column is the subject index and second column contains the corresponding distances to k^{th} NN subjects.

kNNdist returns the distances between subjects and their k NNs. The output is an n \times (k+1) matrix where n is the data size and first column is the subject index and the remaining k columns contain the corresponding distances to k NN subjects.

Usage

kthNNdist(x, k, is.ipd = TRUE, ...)

kNNdist(x, k, is.ipd = TRUE, ...)

Arguments

x	The IPD matrix (if is.ipd=TRUE) or a data set of points in matrix or data frame form where points correspond to the rows (if is.ipd = FALSEALSE).
k	Integer specifying the number of NNs (of subjects).
is.ipd	A logical parameter (default=TRUE). If TRUE, x is taken as the inter-point distance matrix, otherwise, x is taken as the data set with rows representing the data points.
...	are for further arguments, such as method and p, passed to the dist function.

Value

kthNNdist returns an n \times 2 matrix where n is data size (i.e. number of subjects) and first column is the subject index and second column is the k^{th} NN distances.

kNNdist returns an n \times (k+1) matrix where n is data size (i.e. number of subjects) and first column is the subject index and the remaining k columns contain the corresponding distances to k NN subjects.

Author(s)

Elvan Ceyhan

See Also

NNdist and NNdist2cl

Examples

#Examples for kthNNdist
#3D data points, gives NAs when n<=k
n<-20  #or try sample(1:20,1)
Y<-matrix(runif(3*n),ncol=3)
ipd<-ipd.mat(Y)
kthNNdist(ipd,3)
kthNNdist(Y,3,is.ipd = FALSE)
kthNNdist(ipd,5)
kthNNdist(Y,5,is.ipd = FALSE)
kthNNdist(Y,3,is.ipd = FALSE,method="max")

#1D data points
X<-as.matrix(runif(5)) # need to be entered as a matrix with one column
#(i.e., a column vector), hence X<-runif(5) would not work
ipd<-ipd.mat(X)
kthNNdist(ipd,3)

#Examples for kNNdist
#3D data points, gives NAs if n<=k for n,n+1,...,kNNs
n<-20  #or try sample(1:20,1)
Y<-matrix(runif(3*n),ncol=3)
ipd<-ipd.mat(Y)
kNNdist(ipd,3)
kNNdist(ipd,5)
kNNdist(Y,5,is.ipd = FALSE)

kNNdist(Y,5,is.ipd = FALSE,method="max")

kNNdist(ipd,1)
kthNNdist(ipd,1)

#1D data points
X<-as.matrix(runif(5)) # need to be entered as a matrix with one column
#(i.e., a column vector), hence X<-runif(5) would not work
ipd<-ipd.mat(X)
kNNdist(ipd,3)

nnspat documentation built on Aug. 30, 2022, 9:06 a.m.