graph.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.
graph.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.