# pairdist

##### Pairwise distances

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

- Keywords
- spatial

##### Usage

```
pairdist(X, ..., method="C")
pairdist.ppp(X, ..., method="C")
pairdist.default(X, Y=NULL, ..., method="C")
```

##### Arguments

- X,Y
- Arguments specifying the locations of a set of points.
For
`pairdist.ppp`

, the argument`X`

should be a point pattern (object of class`"ppp"`

). For`pairdist.default`

, typically`X`

and < - ...
- Ignored by
`pairdist.ppp`

and`pairdist.default`

. - method
- String specifying which method of calculation to use.
Values are
`"C"`

and`"interpreted"`

. Usually not specified.

##### Details

This function computes the Euclidean distances between all pairs of points, and returns the matrix of distances.

The function `pairdist`

is generic, with
a method for point patterns (objects of class `"ppp"`

)
and a default method.

The method for point patterns expects a single
point pattern argument `X`

and returns the matrix of its
pairwise distances.

The default method expects that `X`

and `Y`

will 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.
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

##### Examples

```
data(cells)
d <- pairdist(cells)
x <- runif(100)
y <- runif(100)
d <- pairdist(x, y)
```

*Documentation reproduced from package spatstat, version 1.6-5, License: GPL version 2 or newer*