# pairdist.psp: Pairwise distances between line segments

### Description

Computes the matrix of distances between all pairs of line segments in a line segment pattern.

### Usage

 ```1 2``` ``` ## S3 method for class 'psp' pairdist(X, ..., method="C", type="Hausdorff") ```

### Arguments

 `X` A line segment pattern (object of class `"psp"`). `...` Ignored. `method` String specifying which method of calculation to use. Values are `"C"` and `"interpreted"`. Usually not specified. `type` Type of distance to be computed. Options are `"Hausdorff"` and `"separation"`. Partial matching is used.

### Details

This function computes the distance between each pair of line segments in `X`, and returns the matrix of distances.

This is a method for the generic function `pairdist` for the class `"psp"`.

The distances between line segments are measured in one of two ways:

• if `type="Hausdorff"`, distances are computed in the Hausdorff metric. The Hausdorff distance between two line segments is the maximum distance from any point on one of the segments to the nearest point on the other segment.

• if `type="separation"`, distances are computed as the minimum distance from a point on one line segment to a point on the other line segment. For example, line segments which cross over each other have separation zero.

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 compiled `C` code is used, which is somewhat faster.

### Value

A square matrix whose `[i,j]` entry is the distance between the line segments numbered `i` and `j`.

### Author(s)

and \rolf

`crossdist`, `nndist`, `pairdist.ppp`

### Examples

 ```1 2 3``` ``` L <- psp(runif(10), runif(10), runif(10), runif(10), owin()) D <- pairdist(L) S <- pairdist(L, type="sep") ```

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