# Count the number of isomorphic mappings between two graphs

Source:`R/topology.R`

`count_isomorphisms.Rd`

Count the number of isomorphic mappings between two graphs

## Arguments

- graph1
The first graph.

- graph2
The second graph.

- method
Currently only ‘vf2’ is supported, see

`isomorphic()`

for details about it and extra arguments.- ...
Passed to the individual methods.

## References

LP Cordella, P Foggia, C Sansone, and M Vento: An improved algorithm
for matching large graphs, *Proc. of the 3rd IAPR TC-15 Workshop
on Graphbased Representations in Pattern Recognition*, 149--159, 2001.

## See also

Other graph isomorphism:
`canonical_permutation()`

,
`count_subgraph_isomorphisms()`

,
`graph_from_isomorphism_class()`

,
`isomorphic()`

,
`isomorphism_class()`

,
`isomorphisms()`

,
`subgraph_isomorphic()`

,
`subgraph_isomorphisms()`

## Examples

```
# colored graph isomorphism
g1 <- make_ring(10)
g2 <- make_ring(10)
isomorphic(g1, g2)
#> [1] TRUE
V(g1)$color <- rep(1:2, length = vcount(g1))
V(g2)$color <- rep(2:1, length = vcount(g2))
# consider colors by default
count_isomorphisms(g1, g2)
#> [1] 10
# ignore colors
count_isomorphisms(g1, g2,
vertex.color1 = NULL,
vertex.color2 = NULL
)
#> [1] 20
```