graph_from_adj_list
Create graphs from adjacency lists
An adjacency list is a list of numeric vectors, containing the neighbor vertices for each vertex. This function creates an igraph graph object from such a list.
- Keywords
- graphs
Usage
graph_from_adj_list(adjlist, mode = c("out", "in", "all", "total"),
duplicate = TRUE)Arguments
- adjlist
The adjacency list. It should be consistent, i.e. the maximum throughout all vectors in the list must be less than the number of vectors (=the number of vertices in the graph). Note that the list is expected to be 0-indexed.
- mode
Character scalar, it specifies whether the graph to create is undirected (‘all’ or ‘total’) or directed; and in the latter case, whether it contains the outgoing (‘out’) or the incoming (‘in’) neighbors of the vertices.
- duplicate
Logical scalar. For undirected graphs it gives whether edges are included in the list twice. E.g. if it is
TRUEthen for an undirected{A,B}edgegraph_from_adj_listexpectsAincluded in the neighbors ofBandBto be included in the neighbors ofA.This argument is ignored if
modeisoutorin.
Details
Adjacency lists are handy if you intend to do many (small) modifications to a graph. In this case adjacency lists are more efficient than igraph graphs.
The idea is that you convert your graph to an adjacency list by
as_adj_list, do your modifications to the graphs and finally
create again an igraph graph by calling graph_from_adj_list.
Value
An igraph graph object.
See Also
Examples
# NOT RUN {
## Directed
g <- make_ring(10, dir=TRUE)
al <- as_adj_list(g, mode="out")
g2 <- graph_from_adj_list(al)
graph.isomorphic(g, g2)
## Undirected
g <- make_ring(10)
al <- as_adj_list(g)
g2 <- graph_from_adj_list(al, mode="all")
graph.isomorphic(g, g2)
ecount(g2)
g3 <- graph_from_adj_list(al, mode="all", duplicate=FALSE)
ecount(g3)
which_multiple(g3)
# }