spatgraph: Compute the edges of a spatial graph
In spatgraphs: Graph Edge Computations for Spatial Point Patterns

spatgraph

R Documentation

Compute the edges of a spatial graph

Description

Given a spatial point pattern, we compute the edges of a graph (network) for a specified type of edge relationship.

Usage

spatgraph(
  x,
  type = "geometric",
  par = NULL,
  verbose = FALSE,
  maxR = 0,
  doDists = FALSE,
  preGraph = NULL
)

Arguments

`x`	Input point pattern object
`type`	Type of the graph
`par`	Parameter(s) for the graph
`verbose`	Print details
`maxR`	Maximum range for edges, helps in large patterns.
`doDists`	Precompute distances? Speeds up some graphs, takes up memory.
`preGraph`	Precomputed graph, taken as a super-graph

Details

Several edge definitions are supported:

geometric: par=numeric>0. Geometric graph, par = connection radius.
knn: par=integer>0. k-nearest neighbours graph, par = k.
mass_geometric: Connect two points if ||x-y||<m(x). par=vector giving the m(x_i)'s
markcross: Connect two points if ||x-y||<m(x)+m(y). par = vector giving the m(x_i)'s
gabriel: Gabriel graph. Additional parameter for allowing par=k instead of 0 points in the circle.
MST: Minimal spanning tree.
SIG: Spheres of Influence.
RST: Radial spanning tree, par=origin of radiation, coordinate vector
RNG: Relative neighbourhood graph
CCC: Class-Cover-Catch, par=factor vector of point types. The factor vector is converted to integers according to R's internal representation of factors, and the points with type 1 will be the target. Use relevel to change the target.

The parameter 'maxR' can be given to bring n^3 graphs closer to n^2. k-nearest neighbours will warn if maxR is too small (<k neighbours for some points), others, like RNG, don't so be careful.

Voronoi diagram aka Delaunay triangulation is not supported as other R-packages can do it, see. e.g. package 'deldir'.

Examples


# basic example
x <- matrix(runif(50*2), ncol=2)
g <- spatgraph(x, "knn", par=3)
plot(g, x)

# bigger example
xb <- matrix(runif(5000*2), ncol=2)
gb <- spatgraph(xb, "RNG", maxR=0.1)

spatgraphs documentation built on Feb. 16, 2023, 8:49 p.m.