# pairdist.default

0th

Percentile

##### Pairwise distances

Computes the matrix of distances between all pairs of points in a set of points in two dimensional space

Keywords
spatial, math
##### Usage
# S3 method for default
pairdist(X, Y=NULL, …, period=NULL, method="C", squared=FALSE)
##### Arguments
X,Y

Arguments specifying 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 x and y, or a matrix with two columns.

Ignored.

period

Optional. Dimensions for periodic edge correction.

method

String specifying which method of calculation to use. Values are "C" and "interpreted". Usually not specified.

squared

Logical. If squared=TRUE, the squared distances are returned instead (this computation is faster).

##### Details

Given the coordinates of a set of points in two dimensional space, 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.

Note: If only pairwise distances within some threshold value are needed the low-level function closepairs may be much faster to use.

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.

For typical input the result is numerically equivalent to (but computationally faster than) as.matrix(dist(x)) where x = cbind(X, Y), but that command is useful for calculating all pairwise distances between points in $k$-dimensional space when x has $k$ 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.

##### Value

A square matrix whose [i,j] entry is the distance between the points numbered i and j.

crossdist, nndist, Kest, closepairs

##### Aliases
• pairdist.default
##### Examples
# NOT RUN {
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)
# }

Documentation reproduced from package spatstat, version 1.61-0, License: GPL (>= 2)

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