# pairdist.ppp

##### Pairwise distances

Computes the matrix of distances between all pairs of points in a point pattern.

##### Usage

```
# S3 method for ppp
pairdist(X, …, 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 numbered `i`

and `j`

.

##### See Also

`pairdist`

,
`pairdist.default`

,
`pairdist.psp`

,
`crossdist`

,
`nndist`

,
`Kest`

##### Examples

```
# NOT RUN {
data(cells)
d <- pairdist(cells)
d <- pairdist(cells, periodic=TRUE)
d <- pairdist(cells, squared=TRUE)
# }
```

*Documentation reproduced from package spatstat, version 1.56-1, License: GPL (>= 2)*