List Triangles in a Graph
Given a list of edges between vertices, compile a list of all triangles formed by these edges.
edges2triangles(iedge, jedge, nvert=max(iedge, jedge), ..., check=TRUE, friendly=rep(TRUE, nvert))
- Integer vectors, of equal length, specifying the edges.
- Number of vertices in the network.
- Logical. Whether to check validity of input data.
- Optional. For advanced use. See Details.
This low level function finds all the triangles (cliques of size 3)
in a finite graph with
nvert vertices and with edges
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 must be integers
from 1 to
To improve efficiency in some applications, the optional argument
friendly can be used. It should be a logical vector of
nvert specifying a labelling of the vertices,
such that two vertices
j,k which are not friendly
friendly[j] = friendly[k] = FALSE)
are never connected by an edge.
- A 3-column matrix of integers, in which each row represents a triangle.
i <- c(1, 2, 5, 5, 1, 4, 2) j <- c(2, 3, 3, 1, 3, 2, 5) edges2triangles(i, j)