The union of two or more graphs are created. The graphs may have identical or overlapping vertex sets.
Usage
# S3 method for class 'igraph'
union(..., byname = "auto")Arguments
- ...
Graph objects or lists of graph objects.
- byname
A logical scalar, or the character scalar
auto. Whether to perform the operation based on symbolic vertex names. If it isauto, that meansTRUEif all graphs are named andFALSEotherwise. A warning is generated ifautoand some (but not all) graphs are named.
Details
union() creates the union of two or more graphs. Edges which are
included in at least one graph will be part of the new graph. This function
can be also used via the %u% operator.
If the byname argument is TRUE (or auto and all graphs
are named), then the operation is performed on symbolic vertex names instead
of the internal numeric vertex ids.
union() keeps the attributes of all graphs. All graph, vertex and
edge attributes are copied to the result. If an attribute is present in
multiple graphs and would result a name clash, then this attribute is
renamed by adding suffixes: _1, _2, etc.
The name vertex attribute is treated specially if the operation is
performed based on symbolic vertex names. In this case name must be
present in all graphs, and it is not renamed in the result graph.
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(),
disjoint_union(),
edge(),
igraph-minus,
intersection(),
intersection.igraph(),
path(),
permute(),
rep.igraph(),
reverse_edges(),
simplify(),
union(),
vertex()
Author
Gabor Csardi csardi.gabor@gmail.com
Examples
## Union of two social networks with overlapping sets of actors
net1 <- graph_from_literal(
D - A:B:F:G, A - C - F - A, B - E - G - B, A - B, F - G,
H - F:G, H - I - J
)
net2 <- graph_from_literal(D - A:F:Y, B - A - X - F - H - Z, F - Y)
print_all(net1 %u% net2)
#> IGRAPH 2931e50 UN-- 13 21 --
#> + attr: name (v/c)
#> + vertex attributes:
#> | name
#> | [1] D
#> | [2] A
#> | [3] B
#> | [4] F
#> | [5] G
#> | [6] C
#> | [7] E
#> | [8] H
#> | [9] I
#> | [10] J
#> | [11] Y
#> | [12] X
#> | [13] Z
#> + edges from 2931e50 (vertex names):
#> [1] I--J H--Z H--I G--H G--E F--X F--Y F--H F--C F--G B--E B--G A--X A--C A--F
#> [16] A--B D--Y D--G D--F D--B D--A