outedges

Outgoing edges from node

Syntax

eid = outedges(G,nodeID)

[eid,nid] = outedges(G,nodeID)

Description

eid = outedges(G,nodeID) returns the indices of all outgoing edges from node nodeID in graph G.

[eid,nid] = outedges(G,nodeID) additionally returns the successor nodes nid that are connected to nodeID by the edges eid.

Examples

Outgoing Edges of Selected Node

Create an undirected multigraph with three nodes and four edges. Find the outgoing edges of node 2.

G = graph([1 1 1 2],[2 2 3 3]);
G.Edges

ans=4×1 table
    EndNodes
    ________

     1    2 
     1    2 
     1    3 
     2    3 

eid = outedges(G,2)

eid = 3×1

     1
     2
     4

The vector eid contains indices to rows in the G.Edges table. Use the vector to index into G.Edges.

G.Edges(eid,:)

ans=3×1 table
    EndNodes
    ________

     1    2 
     1    2 
     2    3 

For undirected graphs, the edges (1,2) and (2,1) are the same.

Find Outgoing Edges and Node Successors

Plot a graph and highlight the outgoing edges and successors of a selected node.

Create and plot a directed graph using the bucky adjacency matrix. Highlight node 10 for reference.

G = digraph(bucky);
p = plot(G);
highlight(p,10,'NodeColor','r','MarkerSize',10)

Determine the outgoing edges and successors of node 10. Highlight these nodes and edges.

[eid,nid] = outedges(G,10)

eid = 3×1

    28
    29
    30

nid = 3×1

     6
     9
    12

X = G.Edges(eid,:)

X=3×2 table
    EndNodes    Weight
    ________    ______

    10     6      1   
    10     9      1   
    10    12      1   

highlight(p,nid,'NodeColor','g','MarkerSize',9)
highlight(p,'Edges',eid,'EdgeColor','g')

Input Arguments

G — Input graph

graph object | digraph object

Input graph, specified as either a graph or digraph object. Use graph to create an undirected graph or digraph to create a directed graph.

Example: G = graph(1,2)

Example: G = digraph([1 2],[2 3])

nodeID — Node identifier

node index | node name

Node identifier, specified as one of the values in this table.

Value	Example
Scalar node index	1
Character vector node name	'A'
String scalar node name	"A"

Example: outedges(G,1)

Example: outedges(G,'A')

Output Arguments

eid — Edge indices

column vector

Edge indices, returned as a column vector. You can use the edge indices to index into the edges table of the graph with G.Edges(eid,:).

nid — Node IDs of successors

node indices | node names

Node IDs of successors, returned as node indices if nodeID is numeric, or as node names if nodeID is a node name. Use findnode(G,nid) to convert node names into node indices. You can use node indices to index into the nodes table of the graph with G.Nodes(nid,:).

The node IDs in nid are the same as those returned by the successors function. However, if there are multiple outgoing edges to the same node, this node is listed more than once in nid.

Tips

• By convention, for undirected graphs, all edges incident to a node are considered to be outgoing edges. Use inedges to find incoming edges in a directed graph.

• For graphs with multiple edges, outedges and successors can return arrays of different lengths, since there can be multiple outgoing edges to some of the successors.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• The node identifier nodeID must be a numeric node index of the input graph G. Node name is not supported.

Version History

Introduced in R2018a