isomorphisms: Calculate all isomorphic mappings between the vertices of two...

In igraph: Network Analysis and Visualization

Calculate all isomorphic mappings between the vertices of two graphs

Description

Calculate all isomorphic mappings between the vertices of two graphs

Usage

isomorphisms(graph1, graph2, method = "vf2", ..., callback = NULL)

Arguments

graph1	The first graph.
graph2	The second graph.
method	Currently only ‘vf2’ is supported, see isomorphic() for details about it and extra arguments.
...	Extra arguments, passed to the various methods.
callback	Optional callback function to call for each isomorphism found. If provided, the function should accept two arguments: map12 (integer vector mapping vertex IDs from graph1 to graph2, 1-based indexing) and map21 (integer vector mapping vertex IDs from graph2 to graph1, 1-based indexing). The function should return FALSE to continue the search or TRUE to stop it. If NULL (the default), all isomorphisms are collected and returned as a list. Only supported for method = "vf2". Important limitation: Callback functions must NOT call any igraph functions (including simple queries like vcount() or ecount()). Doing so will cause R to crash due to reentrancy issues. Extract any needed graph information before calling the function with a callback, or use collector mode (the default) and process results afterward.

Value

If callback is NULL, returns a list of vertex sequences, corresponding to all mappings from the first graph to the second. If callback is provided, returns NULL invisibly.

Related documentation in the C library

get_isomorphisms_vf2(), vcount(), edges(), get_eids(), ecount()

See Also

Other graph isomorphism: canonical_permutation(), count_isomorphisms(), count_subgraph_isomorphisms(), graph_from_isomorphism_class(), isomorphic(), isomorphism_class(), subgraph_isomorphic(), subgraph_isomorphisms()

igraph documentation built on May 4, 2026, 9:07 a.m.