If you want the links to be directional, and have the Bioinformatics toolbox, you can create a biograph
object. This also allows for labelling the nodes with identification strings if you so desire, see the help file. If not they'll be called "Node 1", "Node 2", etc. You'll need to convert your list of links to an adjacency matrix - @RTL gave the accumarray
version, you can also use sub2ind:
N = 4;
adj = zeros(N);
adj(sub2ind([N,N], A(:,1),A(:,2))) = 1;
bg = biograph(adj); % make biograph object
dolayout(bg); % automatically calculate positions for nodes
view(bg); % what it says on the tin
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