spatstat (version 1.31-3)

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)

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.

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.

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)