spatstat.geom (version 3.3-2)

edges2vees: List Dihedral Triples in a Graph

Description

Given a list of edges between vertices, compile a list of all ‘vees’ or dihedral triples formed by these edges.

Usage

edges2vees(iedge, jedge, nvert=max(iedge, jedge), ...,
                check=TRUE)

Value

A 3-column matrix of integers, in which each row represents a triple of vertices, with the first vertex joined to the other two vertices.

Arguments

iedge,jedge

Integer vectors, of equal length, specifying the edges.

nvert

Number of vertices in the network.

...

Ignored

check

Logical. Whether to check validity of input data.

Author

Adrian Baddeley

and Rolf Turner

Details

Given a finite graph with nvert vertices and with edges specified by iedge, jedge, this low-level function finds all ‘vees’ or ‘dihedral triples’ in the graph, that is, all triples of vertices (i,j,k) where i and j are joined by an edge and i and k are joined by an edge.

The interpretation of iedge, jedge is that each successive pair of entries specifies an edge in the graph. The \(k\)th edge joins vertex iedge[k] to vertex jedge[k]. Entries of iedge and jedge must be integers from 1 to nvert.

See Also

edges2triangles

Examples

 i <- c(1, 2, 5, 5, 1, 4, 2)
 j <- c(2, 3, 3, 1, 3, 2, 5)
 edges2vees(i, j)