The vertices of a graph are just singletons that can be indexed by numbers, letters, or even in some cases something as exotic as a monomial. These form the base of a graph; the edges are 2 member subsets of the vertex set of a graph.
i1 : D = digraph({{1,2},{2,1},{3,1}},EntryMode=>"edges");
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i2 : vertexSet D; |
i3 : G = completeGraph 4; |
i4 : vertexSet G
o4 = {0, 1, 2, 3}
o4 : List
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i5 : A = adjacencyMatrix G;
4 4
o5 : Matrix ZZ <--- ZZ
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i6 : graph({a,b,c,d}, A)
o6 = Graph{a => {b, c, d}}
b => {a, c, d}
c => {a, b, d}
d => {a, b, c}
o6 : Graph
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The object vertexSet is a method function.