63.46 InducedSubgraph

InducedSubgraph( gamma, V )
InducedSubgraph( gamma, V, G )

This function returns the subgraph of gamma induced on the vertex list V (which must not contain repeated elements). If the optional third parameter G is given, then it is assumed that G fixes V setwise, and is a group of automorphisms of the induced subgraph when restriced to V. This knowledge is then used to give an associated group to the induced subgraph. If no such G is given then the associated group is trivial.

    gap> gamma := JohnsonGraph(4,2);;
    gap> S := [2,3,4,5];;
    gap> InducedSubgraph( gamma, S, Stabilizer(gamma.group,S,OnSets) );
    rec(
      isGraph := true,
      order := 4,
      group := Group( (2,3), (1,2)(3,4) ),
      schreierVector := [ -1, 2, 1, 2 ],
      adjacencies := [ [ 2, 3 ] ],
      representatives := [ 1 ],
      isSimple := true,
      names := [ [ 1, 3 ], [ 1, 4 ], [ 2, 3 ], [ 2, 4 ] ] ) 

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