MATLAB: Question on using addedge()

graphMATLAB

How do we use addedge to assign weights to a graph containing edges with multiple edge weigths(Value1 and Value2, in my example)?

tail = [1 2 3 4];
head = [2 3 4 5];
G = graph(tail,head)
G.Edges.Value1 = ones(4,1) 
 G.Edges.Value2 = zeros(4,1)    
G = addedge(G,5,6,1) %I want to assign 1 to Value1 to the new edge created between nodes 5,6

I obtain the following error.

Error using graph/addedge (line 139)
Unable to add weighted edges to an unweighted graph.

Any suggestions?

Best Answer

Do you mean:

G = addedge(G,5,6)
G.Edges.Value1 = ones(5,1)

T = table(1, 0, 'VariableNames', {'Value1', 'Value2'});
G = addedge(G, 5, 6, T)

Related Solutions

MATLAB: Modify the weight of few edges in Graph

Don't try to index individual rows of the Edges table to modify properties of the edges. [You could view individual rows of the Edges table using indexing as shown in the "Add Edge Weights" example on this documentation page but you can't change them.] Access the variable inside the table then index individual rows of that variable.

G.Edges.Value(edgepath, :) = [2, 2]
G.Edges % Show the updated table

If you were doing this just so you could increase the width of the lines used to draw those edges, you could use the highlight function on the plotted graph instead.

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)

Best Answer

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MATLAB: Modify the weight of few edges in Graph

MATLAB: Delete and add new edges in a graph

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