BUILT-IN MATHEMATICA SYMBOL

EdgeIndex

gives the integer index for the edge e in the graph g.

EdgeIndex gives the ordering used in functions such as EdgeList and IncidenceMatrix.

Find the integer index of an edge:

The index corresponds to the position in the edge list:

Find the integer index of an edge:

Out[1]=

Out[2]=

The index corresponds to the position in the edge list:

Out[3]=

EdgeIndex works with undirected graphs:

Directed graphs:

returns unevaluated if item is not an edge of g:

EdgeIndex works with large graphs:

Compare performance with a direct search in EdgeList[g]:

The EdgeIndex of an edge corresponds to its position in EdgeList:

Sort the vertices in undirected edges for comparison:

EdgeIndex is typically faster than Position:

EdgeQ can be used to tell whether EdgeIndex will succeed:

Try an edge item:

Try a non-edge item:

Use VertexIndex to find the integer index of a vertex:

VertexIndex and EdgeIndex give the row and column ordering used in IncidenceMatrix:

Test whether

is incident to

:

Some edges do not seem to have integer indices:

Membership is tested using SameQ rather than Equal:

By using identical expressions the integer index is found: