connected.lpp: Connected Components of a Point Pattern on a Linear Network

Description

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

Usage

# S3 method for lpp
connected(X, R=Inf, …, dismantle=TRUE)

Arguments

A linear network (object of class "lpp").

Threshold distance. Pairs of points will be joined together if they are closer than R units apart, measured by the shortest path in the network. The default R=Inf implies that points will be joined together if they are mutually connected by any path in the network.

dismantle

Logical. If TRUE (the default), the network itself will be divided into its path-connected components using connected.linnet.

…

Ignored.

Value

A point pattern (of class "lpp") with marks indicating the grouping, or a list of such point patterns.

Details

The function connected is generic. This is the method for point patterns on a linear network (objects of class "lpp"). It divides the point pattern X into one or more groups of points.

If R=Inf (the default), then X is divided into groups such that any pair of points in the same group can be joined by a path in the network.

If R is a finite number, then two points of X are declared to be R-close if they lie closer than R units apart, measured by the length of the shortest path in the network. Two points are R-connected if they can be reached by a series of steps between R-close pairs of points of X. Then X is divided into groups such that any pair of points in the same group is R-connected.

If dismantle=TRUE (the default) the algorithm first checks whether the network is connected (i.e. whether any pair of vertices can be joined by a path in the network), and if not, the network is decomposed into its connected components.

Examples

Run this code

# NOT RUN {
   ## behaviour like connected.ppp
   U <- runiflpp(20, simplenet)
   plot(connected(U, 0.15, dismantle=FALSE))

   ## behaviour like connected.owin
   ## remove some edges from a network to make it disconnected
   plot(simplenet, col="grey", main="", lty=2)
   A <- thinNetwork(simplenet, retainedges=-c(3,5))
   plot(A, add=TRUE, lwd=2)
   X <- runiflpp(10, A)
   ## find the connected components
   cX <- connected(X)
   plot(cX[[1]], add=TRUE, col="blue", lwd=2)
# }