# pairdist.default

##### Pairwise distances

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

##### Usage

```
## S3 method for class 'default':
pairdist(X, Y=NULL, \dots, 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 - ...
- 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,
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.

##### Value

- A square matrix whose
`[i,j]`

entry is the distance between the points numbered`i`

and`j`

.

##### See Also

##### Examples

```
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 1.17-0, License: GPL (>= 2)*