MATLAB: How to add nodes and edges

graph

p = [3,2,1];
for i = 1:length(p)
last_element = p(end);
G = graph();
H = addnode(G,last_element);
*HOW TO ADD EDGE??? HERE ??*
p(end) = [];  % REMOVING THE LAST ELEMENT ONCE ADDED TO THE GRAPH so in 2nd iteration p = [3,2]
end
plot(H);

Best Answer

You can use addedge() to add edges.

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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 does Matlab produce thin edges

edge() takes a grayscale edge image like you'd get with imgradient(), and then thresholds it and skeletonizes the thresholded image, like you'd get with bwmorph(BW, 'Skel', inf).

Best Answer

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MATLAB: Delete and add new edges in a graph

MATLAB: How does Matlab produce thin edges

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