MATLAB: Graph theory – remove several edges

codegraphgraph theoryMATLAB

Hi all, I have graph consists of 37 edges and 33 nodes, I want to remove some edges . removing 1 edge works with me

R33=graph(A33);

G = rmedge(R33,18,33) ; % remove branch from node 18 to 33

plot(G)

However, when i tried to remove several edges it did not work. can any one help

R33=graph(A33);

G = rmedge(R33, [18 33], [25 29], [12 22]) ; % could not remove these branches 18-33 , 25-29 , 12-22

plot(G)

can anyone help

thank you

Best Answer

Looking at its documentation page the rmedge function for graph objects does not have a syntax that accepts four input arguments. However, the s and t inputs to rmedge can be vectors of node indices or a cell or string array of node names to delete multiple edges at once. See the "Remove Edges with Specified End Nodes" example on that page.

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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: How to find all the downstream nodes from a node in a graph

Gc = G;
[eid, nid] = outedges(Gc,1);
Gc = rmedge(Gc, eid(nid ~= 2));
downstream_nodes = setdiff(unique(minspantree(Gc,'Root',1).Edges.EndNodes), 1);

Best Answer

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MATLAB: Delete and add new edges in a graph

MATLAB: How to find all the downstream nodes from a node in a graph

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