subgraph
Extract subgraph
Description
Examples
Extract Subgraph
Create and plot a graph.
s = [1 1 1 1 2 2 2 2 2 2 2 2 2 2 15 15 15 15 15]; t = [3 5 4 2 14 6 11 12 13 10 7 9 8 15 16 17 19 18 20]; G = graph(s,t); plot(G,'Layout','force')
Extract a subgraph from G
by specifying which nodes to include. The node numbering in the subgraph is reset.
idx = [2 15 16 17 18 19 20 1 3 4 5]; H = subgraph(G,idx); plot(H,'Layout','force')
Subgraph with Node and Edge Properties
Create and plot a weighted graph with named nodes.
s = [1 1 1 2 2 2 8 8 8 8]; t = [2 3 4 5 6 7 9 10 11 12]; weights = [10 30 40 80 60 60 20 30 90 80]; names = {'A' 'B' 'C' 'D' 'E' 'F' 'G' 'H' 'I' 'J' 'K' 'L'}; G = graph(s,t,weights,names); plot(G,'EdgeLabel',G.Edges.Weight)
Extract a subgraph that contains node 'B'
and all of its neighbors. subgraph
preserves the node names and edge weights. However, the numeric node IDs in H
are renumbered compared to G
.
N = neighbors(G,'B'); H = subgraph(G, ['B'; N]); plot(H,'EdgeLabel',H.Edges.Weight)
Input Arguments
nodeIDs
— Node identifiers
node indices | node names
Node identifiers, specified as one or more node indices or node names.
nodeIDs
selects a subset of the nodes in
G
to generate the subgraph,
H
.
This table shows the different ways to refer to one or more nodes either by their numeric node indices or by their node names.
Form | Single Node | Multiple Nodes |
---|---|---|
Node index | Scalar Example: | Vector Example: |
Node name | Character vector Example: | Cell array of character vectors Example: |
String scalar Example: | String array Example: |
Example: H = subgraph(G,[1 2 5])
Example: H = subgraph(G,{'A' 'B' 'E'})
idx
— Node selection vector
vector
Node selection vector, specified as a logical vector. The subgraph
contains only the nodes J
for which
idx(J)
is logical 1
(true
). The index of node J
in
H
is I(J)
, where I =
find(idx)
.
Example: subgraph(G,degree(G)>2)
Data Types: logical
Output Arguments
H
— Subgraph
graph
object | digraph
object
Subgraph, returned as a graph
or
digraph
object. H
contains only
the nodes that were selected with nodeIDs
or
idx
. Other nodes in G
(and the
edges connecting to those nodes) are discarded. The node properties and edge
properties of the selected nodes and edges are carried over from
G
into H
.
See graph
or digraph
for more information
about graph objects.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Usage notes and limitations:
The node identifiers
nodeIDs
must be node indices of the input graphG
. Node names are 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 R2015b
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