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Intersection of graphs

Source: R/operators.R
intersection.igraph.Rd

The intersection of two or more graphs are created. The graphs may have identical or overlapping vertex sets.

Usage

# S3 method for class 'igraph'
intersection(
  ...,
  byname = "auto",
  keep.all.vertices = TRUE,
  graph.attr.comb = igraph_opt("graph.attr.comb"),
  vertex.attr.comb = "rename",
  edge.attr.comb = "rename"
)

Arguments

...

Graph objects or lists of graph objects.

byname

A Logical, or the character scalar auto. Whether to perform the operation based on symbolic vertex names. If it is auto, that means TRUE if all graphs are named and FALSE otherwise. A warning is generated if auto and some (but not all) graphs are named.

keep.all.vertices

Logical, whether to keep vertices that only appear in a subset of the input graphs.

graph.attr.comb, vertex.attr.comb, edge.attr.comb

Specification for combining clashing graph, vertex and edge attributes. vertex.attr.comb and edge.attr.comb default to "rename"; graph.attr.comb defaults to the graph.attr.comb igraph option ("rename" unless changed via igraph_options()). See igraph-attribute-combination for the available combiners.

Value

A new graph object.

Details

intersection() creates the intersection of two or more graphs: only edges present in all graphs will be included. The corresponding operator is %s%.

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.

intersection() keeps the attributes of all graphs. All graph, vertex and edge attributes are copied to the result. By default, if an attribute is present in multiple graphs and would result in a name clash, that attribute is renamed by adding suffixes: _1, _2, etc. Pass graph.attr.comb, vertex.attr.comb or edge.attr.comb to combine clashing attributes instead; see igraph-attribute-combination for the available combiners.

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.

vcount(), permute_vertices(), edges(), get_eids(), ecount()

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(), path(), permute(), rep.igraph(), reverse_edges(), simplify(), transitive_closure(), union(), union.igraph(), vertex()

Author

Gabor Csardi csardi.gabor@gmail.com

Examples


## Common part of two social networks
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 %s% net2)
#> ── <igraph> ───────────────────────────────────────────────────────── bd31097 ──
#> ℹ undirected · named
#> ℹ 13 vertices · 4 edges
#> 
#> ── Attributes ──────────────────────────────────────────────────────────────────
#> → vertex: name <chr>
#> 
#> ── 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 (vertex names) ────────────────────────────────────────────────────────
#> [1] F ─ H  A ─ B  D ─ F  D ─ A