This is an S3 generic function. See methods("union")
for the actual implementations for various S3 classes. Initially
it is implemented for igraph graphs and igraph vertex and edge
sequences. See
union.igraph, and
union.igraph.vs.
Usage
union(...)
Arguments
...
Arguments, their number and interpretation depends on
the function that implements union.
Value
Depends on the function that implements this method.