inedges

Incoming edges to node

Syntax

eid = inedges(G,nodeID)

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

Description

eid = inedges(G,nodeID) returns the indices of all incoming edges to node nodeID in directed graph G.

[eid,nid] = inedges(G,nodeID) additionally returns the node IDs of the predecessor nodes connected to nodeID by the edges in eid.

Examples

Incoming Edges of Selected Node

Create a multigraph with three nodes and four edges. Find the incoming edges of node 3.

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

ans=4×1 table
    EndNodes
    ________

     1    2 
     1    2 
     1    3 
     2    3 

eid = inedges(G,3)

eid = 2×1

     3
     4

G.Edges(eid,:)

ans=2×1 table
    EndNodes
    ________

     1    3 
     2    3 

Find Incoming Edges and Node Predecessors

Plot a graph and highlight the incoming edges and predecessors of a selected node.

Create and plot a directed graph using the bucky adjacency matrix. Highlight node 1 for reference.

G = digraph(bucky);
p = plot(G);
highlight(p,1,'NodeColor','r','MarkerSize',10)

Determine the incoming edges and predecessors of node 1. Highlight these nodes and edges.

[eid,nid] = inedges(G,1)

eid = 3×1

     4
    13
    16

nid = 3×1

     2
     5
     6

X = G.Edges(eid,:)

X=3×2 table
    EndNodes    Weight
    ________    ______

     2    1       1   
     5    1       1   
     6    1       1   

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

Input Arguments

G — Input graph

digraph object

Input graph, specified as a digraph object. Use digraph to create a directed graph object.

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: inedges(G,1)

Example: inedges(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 predecessors

node indices | node names

Node IDs of predecessors, 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 predecessors function. However, if there are multiple incoming edges from 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 outedges with undirected graphs.

• For graphs with multiple edges, inedges and predecessors can return arrays of different lengths, since there can be multiple incoming edges from some of the predecessors.

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.

Thread-Based Environment
Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

Version History

Introduced in R2018a