pairdist.default {spatstat} | R Documentation |
Computes the matrix of distances between all pairs of points in a set of points
## Default S3 method: pairdist(X, Y=NULL, ..., period=NULL, method="C", squared=FALSE)
X,Y |
Arguments specifying the coordinates of a set of points.
Typically |
... |
Ignored. |
period |
Optional. Dimensions for periodic edge correction. |
method |
String specifying which method of calculation to use.
Values are |
squared |
Logical. If |
Given the coordinates of a set of points,
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
.
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.
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.
A square matrix whose [i,j]
entry is the distance
between the points numbered i
and j
.
Pavel Grabarnik pavel.grabar@issp.serpukhov.su and Adrian Baddeley Adrian.Baddeley@csiro.au http://www.maths.uwa.edu.au/~adrian/
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)