spatstat (version 1.41-1)

linnet: Create a Linear Network

Description

Creates an object of class "linnet" representing a network of line segments.

Usage

linnet(vertices, m, edges, sparse=FALSE)

Arguments

vertices

Point pattern (object of class "ppp") specifying the vertices of the network.

m

Adjacency matrix. A matrix or sparse matrix of logical values equal to TRUE when the corresponding vertices are joined by a line. (Specify either m or edges.)

edges

Edge list. A two-column matrix of integers, specifying all pairs of vertices that should be joined by an edge. (Specify either m or edges.)

sparse

Optional. Logical value indicating whether to use a sparse matrix representation of the network. See Details.

Value

• Object of class "linnet" representing the linear network.

Details

An object of class "linnet" represents a network of straight line segments in two dimensions. The function linnet creates such an object from the minimal information: the spatial location of each vertex (endpoint, crossing point or meeting point of lines) and information about which vertices are joined by an edge.

If sparse=FALSE (the default), the algorithm will compute and store various properties of the network, including the adjacency matrix m and a matrix giving the shortest-path distances between each pair of vertices in the network. This is more efficient for small datasets. However it can require large amounts of memory and can take a long time to execute.

If sparse=TRUE, then the shortest-path distances will not be computed, and the network adjacency matrix m will be stored as a sparse matrix. This saves a lot of time and memory when creating the linear network.

See Also

simplenet for an example of a linear network.

methods.linnet for methods applicable to linnet objects.

delaunay.network. ppp, psp.

Examples

# letter 'A' specified by adjacency matrix
  v <- ppp(x=(-2):2, y=3*c(0,1,2,1,0), c(-3,3), c(-1,7))
  m <- matrix(FALSE, 5,5)
  for(i in 1:4) m[i,i+1] <- TRUE
  m[2,4] <- TRUE
  m <- m | t(m)
  letterA <- linnet(v, m)
  plot(letterA)

  # letter 'A' specified by edge list
  edg <- cbind(1:4, 2:5)
  edg <- rbind(edg, c(2,4))
  letterA <- linnet(v, edges=edg)