Hypergraphs
Transversal
Return the transversal of an hypergraph
Calling Sequence
Parameters
Description
Examples
References
Compatibility
Transversal(H)
H
-
Hypergraph
The command Transversal(H) returns the transversal hypergraph of H.
Terminology
Transversal : If H :=(X, Y) is a hypergraph, then a subset S of X is transversal to H whenever S has a non-empty intersection with every hyperedge of H. If H :=(X, Y) is a hypergraph, then the transversal hypergraph of H is the hypergraph (X, Z) where Z consists of all transversals to H that are minimal w.r.t. inclusion.
with⁡Hypergraphs:with⁡ExampleHypergraphs
Fan,Kuratowski,Lovasz,NonEmptyPowerSet,RandomHypergraph
Create a hypergraph from its vertices and edges.
H≔Hypergraph⁡1,2,3,4,5,6,7,1,2,3,2,3,4,3,5,6
H≔< a hypergraph on 7 vertices with 4 hyperedges >
Print the vertices and edges of H.
Vertices⁡H;Hyperedges⁡H
1,2,3,4,5,6,7
4,2,3,1,2,3,3,5,6
Draw a graphical representation of this hypergraph.
Draw⁡H
Compute Max(H), print its vertices and edges, draw a graphical representation of it.
M≔Max⁡H;Vertices⁡M;Hyperedges⁡M;Draw⁡M
M≔< a hypergraph on 7 vertices with 3 hyperedges >
4,1,2,3,3,5,6
Compute Min(H), print its vertices and edges, draw a graphical representation of it.
M≔Min⁡H;Vertices⁡M;Hyperedges⁡M;Draw⁡M
4,2,3,3,5,6
Compute the transversal hypergraph of H.
T≔Transversal⁡H;Vertices⁡T;Hyperedges⁡T;Draw⁡T
T≔< a hypergraph on 7 vertices with 3 hyperedges >
3,4,2,4,5,2,4,6
Observe that Transversal(T) and Min(H) are equal.
TT≔Transversal⁡T;Hyperedges⁡TT;AreEqual⁡TT,Min⁡H
TT≔< a hypergraph on 7 vertices with 3 hyperedges >
true
Consider the following Kuratowski hypergraph.
K3≔Kuratowski⁡1,2,3,4,5,3
K3≔< a hypergraph on 5 vertices with 10 hyperedges >
Observe that K3 is its own transversal.
AreEqual⁡Transversal⁡K3,K3
Consider a random hypergraph on 5 points and 15 hyperedges.
R≔RandomHypergraph⁡5,15;Hyperedges⁡R
R≔< a hypergraph on 5 vertices with 15 hyperedges >
5,1,2,2,3,1,4,2,4,1,5,2,5,3,5,1,3,4,1,3,5,2,3,5,1,4,5,3,4,5,1,2,3,5,1,2,4,5
Compute its minimal hyperedges.
M≔Min⁡R;Hyperedges⁡M
M≔< a hypergraph on 5 vertices with 5 hyperedges >
5,1,2,2,3,1,4,2,4
Compute the transversal hypergraph T of R and the transversal hypergraph TT of T.
T≔Transversal⁡R;Hyperedges⁡T
T≔< a hypergraph on 5 vertices with 3 hyperedges >
1,2,5,2,4,5,1,3,4,5
TT≔Transversal⁡T;Hyperedges⁡TT
TT≔< a hypergraph on 5 vertices with 5 hyperedges >
Observe that TT and M are equal.
AreEqual⁡TT,M
Claude Berge. Hypergraphes. Combinatoires des ensembles finis. 1987, Paris, Gauthier-Villars, translated to English.
Claude Berge. Hypergraphs. Combinatorics of Finite Sets. 1989, Amsterdam, North-Holland Mathematical Library, Elsevier, translated from French.
Charles Leiserson, Liyun Li, Marc Moreno Maza and Yuzhen Xie " Parallel computation of the minimal elements of a poset." Proceedings of the 4th International Workshop on Parallel Symbolic Computation (PASCO) 2010: 53-62, ACM.
The Hypergraphs[Transversal] command was introduced in Maple 2024.
For more information on Maple 2024 changes, see Updates in Maple 2024.
See Also
Hypergraphs[AreEqual]
Hypergraphs[Max]
Hypergraphs[Min]
Hypergraphs[Transversal]
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