# crossdist.pp3: Pairwise distances between two different three-dimensional...

### Description

Computes the distances between pairs of points taken from two different three-dimensional point patterns.

### Usage

 ```1 2``` ``` ## S3 method for class 'pp3' crossdist(X, Y, ..., periodic=FALSE, squared=FALSE) ```

### Arguments

 `X,Y` Point patterns in three dimensions (objects of class `"pp3"`). `...` Ignored. `periodic` Logical. Specifies whether to apply a periodic edge correction. `squared` Logical. If `squared=TRUE`, the squared distances are returned instead (this computation is faster).

### Details

Given two point patterns in three-dimensional space, this function computes the Euclidean distance from each point in the first pattern to each point in the second pattern, and returns a matrix containing these distances.

This is a method for the generic function `crossdist` for three-dimensional point patterns (objects of class `"pp3"`).

This function expects two point patterns `X` and `Y`, and returns the matrix whose `[i,j]` entry is the distance from `X[i]` to `Y[j]`.

Alternatively if `periodic=TRUE`, then provided the windows containing `X` and `Y` are identical and are rectangular, 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.

### Value

A matrix whose `[i,j]` entry is the distance from the `i`-th point in `X` to the `j`-th point in `Y`.

### Author(s)

based on code for two dimensions by Pavel Grabarnik.

`crossdist`, `pairdist`, `nndist`, `G3est`

### Examples

 ```1 2 3 4``` ``` X <- runifpoint3(20) Y <- runifpoint3(30) d <- crossdist(X, Y) d <- crossdist(X, Y, periodic=TRUE) ```

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