Transversal - Maple Help
For the best experience, we recommend viewing online help using Google Chrome or Microsoft Edge.

Online Help

All Products    Maple    MapleSim


Hypergraphs

  

Transversal

  

Return the transversal of an hypergraph

 

Calling Sequence

Parameters

Description

Examples

References

Compatibility

Calling Sequence

Transversal(H)

Parameters

H

-

Hypergraph

Description

• 

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.

Examples

withHypergraphs:withExampleHypergraphs

Fan,Kuratowski,Lovasz,NonEmptyPowerSet,RandomHypergraph

(1)

Create a hypergraph from its vertices and edges.

HHypergraph1,2,3,4,5,6,7,1,2,3,2,3,4,3,5,6

H< a hypergraph on 7 vertices with 4 hyperedges >

(2)

Print the vertices and edges of H.

VerticesH&semi;HyperedgesH

1&comma;2&comma;3&comma;4&comma;5&comma;6&comma;7

4&comma;2&comma;3&comma;1&comma;2&comma;3&comma;3&comma;5&comma;6

(3)

Draw a graphical representation of this hypergraph.

DrawH

Compute Max(H), print its vertices and edges, draw a graphical representation of it.

MMaxH&semi;VerticesM&semi;HyperedgesM&semi;DrawM

M< a hypergraph on 7 vertices with 3 hyperedges >

1&comma;2&comma;3&comma;4&comma;5&comma;6&comma;7

4&comma;1&comma;2&comma;3&comma;3&comma;5&comma;6

Compute Min(H), print its vertices and edges, draw a graphical representation of  it.

MMinH&semi;VerticesM&semi;HyperedgesM&semi;DrawM

M< a hypergraph on 7 vertices with 3 hyperedges >

1&comma;2&comma;3&comma;4&comma;5&comma;6&comma;7

4&comma;2&comma;3&comma;3&comma;5&comma;6

Compute the transversal hypergraph of H.

TTransversalH&semi;VerticesT&semi;HyperedgesT&semi;DrawT

T< a hypergraph on 7 vertices with 3 hyperedges >

1&comma;2&comma;3&comma;4&comma;5&comma;6&comma;7

3&comma;4&comma;2&comma;4&comma;5&comma;2&comma;4&comma;6

Observe that Transversal(T) and Min(H) are equal.

TTTransversalT&semi;HyperedgesTT&semi;AreEqualTT&comma;MinH

TT< a hypergraph on 7 vertices with 3 hyperedges >

4&comma;2&comma;3&comma;3&comma;5&comma;6

true

(4)

Consider the following Kuratowski hypergraph.

K3Kuratowski1&comma;2&comma;3&comma;4&comma;5&comma;3

K3< a hypergraph on 5 vertices with 10 hyperedges >

(5)

Observe that K3 is its own transversal.

AreEqualTransversalK3&comma;K3

true

(6)

Consider a random hypergraph on 5 points and 15 hyperedges.

RRandomHypergraph5&comma;15&semi;HyperedgesR

R< a hypergraph on 5 vertices with 15 hyperedges >

5&comma;1&comma;2&comma;2&comma;3&comma;1&comma;4&comma;2&comma;4&comma;1&comma;5&comma;2&comma;5&comma;3&comma;5&comma;1&comma;3&comma;4&comma;1&comma;3&comma;5&comma;2&comma;3&comma;5&comma;1&comma;4&comma;5&comma;3&comma;4&comma;5&comma;1&comma;2&comma;3&comma;5&comma;1&comma;2&comma;4&comma;5

(7)

Compute its minimal hyperedges.  

MMinR&semi;HyperedgesM

M< a hypergraph on 5 vertices with 5 hyperedges >

5&comma;1&comma;2&comma;2&comma;3&comma;1&comma;4&comma;2&comma;4

(8)

Compute the transversal hypergraph  T of  R and the transversal hypergraph TT of  T.

TTransversalR&semi;HyperedgesT

T< a hypergraph on 5 vertices with 3 hyperedges >

1&comma;2&comma;5&comma;2&comma;4&comma;5&comma;1&comma;3&comma;4&comma;5

(9)

TTTransversalT&semi;HyperedgesTT

TT< a hypergraph on 5 vertices with 5 hyperedges >

5&comma;1&comma;2&comma;2&comma;3&comma;1&comma;4&comma;2&comma;4

(10)

Observe that TT and M are equal.

AreEqualTT&comma;M

true

(11)

References

  

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.

Compatibility

• 

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]