R: Distance Map of Point Pattern

distmap.ppp {spatstat.geom} | R Documentation

## Distance Map of Point Pattern

### Description

Computes the distance from each pixel to the nearest point in the given point pattern.

### Usage

      ## S3 method for class 'ppp'
    distmap(X, ..., metric=NULL)

### Arguments

`X` | A point pattern (object of class `"ppp"`).
`...` | Arguments passed to `as.mask` to control pixel resolution.
`metric` | Optional. A distance metric (object of class `"metric"`, see `metric.object`) which will be used to compute the distances.

### Details

The “distance map” of a point pattern X is the function f whose value `f(u)` is defined for any two-dimensional location u as the shortest distance from u to X.

This function computes the distance map of the point pattern `X` and returns the distance map as a pixel image. The greyscale value at a pixel u equals the distance from u to the nearest point of the pattern `X`.

Additionally, the return value has two attributes, `"index"` and `"bdry"`, which are also pixel images. The grey values in `"bdry"` give the distance from each pixel to the bounding rectangle of the image. The grey values in `"index"` are integers identifying which point of `X` is closest.

This is a method for the generic function `distmap`.

Note that this function gives the distance from the centre of each pixel to the nearest data point. To compute the exact distance from a given spatial location to the nearest data point in `X`, use `distfun` or `nncross`.

### Value

A pixel image (object of class `"im"`) whose greyscale values are the values of the distance map. The return value has attributes `"index"` and `"bdry"` which are also pixel images.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au

and Rolf Turner r.turner@auckland.ac.nz

### See Also

Generic function `distmap` and other methods `distmap.psp`, `distmap.owin`.

Generic function `distfun`.

Nearest neighbour distance `nncross`

### Examples

      data(cells)
      U <- distmap(cells)
      if(interactive()) {
      plot(U)
      plot(attr(U, "bdry"))
      plot(attr(U, "index"))
      }

[Package spatstat.geom version 2.3-2 Index]