pairdist.ppp
Pairwise distances
Computes the matrix of distances between all pairs of points in a point pattern.
Usage
## S3 method for class 'ppp':
pairdist(X, \dots, periodic=FALSE, method="C", squared=FALSE)Arguments
- X
- A point pattern (object of class
"ppp"). - ...
- Ignored.
- periodic
- Logical. Specifies whether to apply a 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
This is a method for the generic function pairdist.
Given a point pattern X (an object of class "ppp"),
this function computes the Euclidean distances between all pairs of
points in X, and returns the matrix of distances.
Alternatively if periodic=TRUE and the window containing X is a
rectangle, then the distances will be computed in the `periodic'
sense (also known as `torus' distance): opposite edges of the
rectangle are regarded as equivalent.
This is meaningless if the window is not a rectangle.
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 numberediandj.
See Also
pairdist,
pairdist.default,
pairdist.psp,
crossdist,
nndist,
Kest
Examples
data(cells)
d <- pairdist(cells)
d <- pairdist(cells, periodic=TRUE)
d <- pairdist(cells, squared=TRUE)