connected.ppp {spatstat.geom}

Connected Components of a Point Pattern

Description

Finds the topologically-connected components of a point pattern, when all pairs of points closer than a threshold distance are joined.

Usage

## S3 method for class 'ppp'
connected(X, R, ...)

## S3 method for class 'pp3'
connected(X, R, ...)

Arguments

X

A point pattern (object of class "ppp" or "pp3").

R

Threshold distance. Pairs of points closer than R units apart will be joined together.

...

Other arguments, not recognised by these methods.

Details

This function can be used to identify clumps of points in a point pattern.

The function connected is generic. This file documents the methods for point patterns in dimension two or three (objects of class "ppp" or "pp3").

The point pattern X is first converted into an abstract graph by joining every pair of points that lie closer than R units apart. Then the connected components of this graph are identified.

Two points in X belong to the same connected component if they can be reached by a series of steps between points of X, each step being shorter than R units in length.

The result is a vector of labels for the points of X where all the points in a connected component have the same label.

Value

A point pattern, equivalent to X except that the points have factor-valued marks, with levels corresponding to the connected components.

Author(s)

Adrian Baddeley [e-mail], Rolf Turner [e-mail] and Ege Rubak [e-mail].

See Also

connected.im, im.object, tess

Examples

   Y <- connected(redwoodfull, 0.1)
   if(interactive()) {
    plot(Y, cols=1:length(levels(marks(Y))),
         main="connected(redwoodfull, 0.1)")
   }
   X <- osteo$pts[[1]]
   Z <- connected(X, 32)
   if(interactive()) {
    plot(Z, col=marks(Z), main="")
   }