The union of two or more graphs are created. The graphs are assumed to have disjoint vertex sets.
Details
disjoint_union() creates a union of two or more disjoint graphs.
Thus first the vertices in the second, third, etc. graphs are relabeled to
have completely disjoint graphs. Then a simple union is created. This
function can also be used via the %du% operator.
disjoint_union() handles graph, vertex and edge attributes. In
particular, it merges vertex and edge attributes using the vctrs::vec_c()
function. For graphs that lack some vertex/edge attribute, the corresponding
values in the new graph are set to a missing value (NA for scalar attributes,
NULL for list attributes). Graph attributes are simply
copied to the result. If this would result a name clash, then they are
renamed by adding suffixes: _1, _2, etc.
Note that if both graphs have vertex names (i.e. a name vertex
attribute), then the concatenated vertex names might be non-unique in the
result. A warning is given if this happens.
An error is generated if some input graphs are directed and others are undirected.
See also
Other functions for manipulating graph structure:
+.igraph(),
add_edges(),
add_vertices(),
complementer(),
compose(),
connect(),
contract(),
delete_edges(),
delete_vertices(),
difference(),
difference.igraph(),
edge(),
igraph-minus,
intersection(),
intersection.igraph(),
path(),
permute(),
rep.igraph(),
reverse_edges(),
simplify(),
union(),
union.igraph(),
vertex()
Author
Gabor Csardi csardi.gabor@gmail.com
Examples
## A star and a ring
g1 <- make_star(10, mode = "undirected")
V(g1)$name <- letters[1:10]
g2 <- make_ring(10)
V(g2)$name <- letters[11:20]
print_all(g1 %du% g2)
#> IGRAPH e224c61 UN-- 20 19 --
#> + attr: name_1 (g/c), name_2 (g/c), mode (g/c), center (g/n), mutual
#> | (g/l), circular (g/l), name (v/c)
#> + edges from e224c61 (vertex names):
#> [1] a--b a--c a--d a--e a--f a--g a--h a--i a--j k--l l--m m--n n--o o--p p--q
#> [16] q--r r--s s--t k--t