Constructing an Adjacency Matrix from a Matrix/Table

I have a matrix, LinkData, whose first 2 columns contains node reference numbers, and the 3rd column contains data that the 2 nodes share. I am trying to create an Adjacency matrix using LinkData. I'm not even completely sure what an Adjacency matrix is let alone construct it. I know that it is supposed to identify which nodes are adjacent to each other (i.e. node 2 is adjacent to node 1 and 3, and node 3 is adjacent to node 2 and 4).

I have tried using accumarray but I do not think I got the right results.

nodesPairs = [LinkData(:,1),LinkData(:,2)] %extract node pairs; 
accumarray(nodesPairs+1,1);

Any help would be deeply appreciated!

Answer 1

[Walter Roberson]

Close, but you should use

nodesPairs = [LinkData(:,1),LinkData(:,2)]; %extract node pairs
nodePairs = [nodePairs; fliplr(nodePairs)];
adj = accumarray(nodePairs+1, 1);

You should also give consideration to,

adj = sparse([LinkData(:,1); LinkData(:,2)]+1, [LinkData(:,2); LinkData(:,1)]+1, 1);

If you have a sufficiently recent MATLAB, then consider

G = graph(nodePairs(:,1), nodePairs(:,2));
adj = adjacency(G);

[Mohammad Bhat]

Then, how to plot the graph..

[Steven Lord]

If you made a graph as per the last section of code in Walter's answer, just plot it.

plot(G)