MATLAB: How created a graph from unordered node list

graphgraph theoryMATLAB

I want to created a graph from an unordered list of nodes. However, Matlab creat graph from ordered node numbers. For example, My node list is as :

source=[1,4,8,7];
Target=[7,8,1,4];

Now this would be the result if I plot the graph from this source and target nodes:

G=graph(source,Target);
P=plot(G);

The results shows the range of nodes from 1 to 8; however, These nodes don't exist in this network. This is problematic since I have a huge road network like this (34000 unordered pairs of source and targets) and each node has and coordiantion. This seroiusly cause problem while I'm trying to plot it with coordiantes. I tried to remove those nodes but it completly changes the graph (I have no Idea why this happening). Thank you in advance for any advice or help.

Best Answer

When a graph or digraph is specified using numbers, the assumption is that all nodes of this graph have numbers from 1:numberOfNodes. This is not the case when a graph or digraph is constructed from strings, so the simplest workaround is

G = graph(string(source), string(Target));

Related Solutions

MATLAB: Delete and add new edges in a graph

A graph object is undirected. A digraph object is directed.

Construct your network graph using digraph instead of graph on the fourth line of your code.

By the way, the addedge function has two capabilities you might find useful.

The s (source) and t (target) inputs can be vectors to add multiple edges at once.
If the source and/or target inputs reference nodes that don't yet exist, addedge adds them.

So you could do this with something like:

% Make a digraph and plot it for later reference
G = digraph(triu(ones(3)));
figure;
plot(G)
% How many nodes does G have?
N = numnodes(G);
% Add 2 new nodes
newnodes = [N+1 N+2];
% Add the edges between 1 and N+1, N+1 and N+2, and N+2 and 2
%

% I'm doing this in a copy of G, rather than G itself so you can go back
% and compare G and G2. But you can modify G itself if you want.
%
% Because of the way I created G, it's a weighted digraph, so I need
% to give the new edges weights. I chose to weight them all pi.
% Scalar expansion lets me specify a scalar weight to be used for each new edge.
G2 = addedge(G, [1 newnodes], [newnodes 2], pi);
% Eliminate the edge from 1 to 2
G2 = rmedge(G2, 1, 2);
% Plot the new digraph
figure;
plot(G2)

MATLAB: Specifying node numbers using digraph

The easiest way to use graph/digraph when your node numbers are not sequential is to convert the node numbers to string, which will have them treated as node names instead. Then, you should be able to use digraph and hte plot command with 'XData', 'YData', and 'ZData' options.

Best Answer

Related Solutions

MATLAB: Delete and add new edges in a graph

MATLAB: Specifying node numbers using digraph

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