R: Distance Map of Line Segment Pattern

distmap.psp {spatstat} | R Documentation

## Distance Map of Line Segment Pattern

### Description

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

### Usage

      ## S3 method for class 'psp'
    distmap(X, ...)

### Arguments

`X` | A line segment pattern (object of class `"psp"`).
`...` | Arguments passed to `as.mask` to control pixel resolution.

### Details

The “distance map” of a line segment 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 line segment 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 line segment of the pattern `X`. Distances are computed using analytic geometry.

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 line segment of `X` is closest.

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

Note that this function gives the exact distance from the centre of each pixel to the nearest line segment. To compute the exact distance from the points in a point pattern to the nearest line segment, use `distfun` or one of the low-level functions `nncross` or `project2segment`.

### 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

`distmap`, `distmap.owin`, `distmap.ppp`, `distfun`, `nncross`, `nearestsegment`, `project2segment`.

### Examples

        a <- psp(runif(20),runif(20),runif(20),runif(20), window=owin())
        Z <- distmap(a)
        plot(Z)
        plot(a, add=TRUE)

[Package spatstat version 1.54-0 Index]