29 lines
866 B
Matlab
29 lines
866 B
Matlab
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% Convert an incidence matrix to an edge list.
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%
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% Inputs: inc - incidence matrix nxm (number of nodes x number of edges)
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% Outputs: edge list - mx3, m x (node 1, node 2, edge weight)
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%
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% Example: [-1; 1] <=> [1,2,1], one directed (1->2) edge
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% GB: last updated, Sep 25 2012
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function el = inc2edgeL(inc)
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m = size(inc,2); % number of edges
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el = zeros(m,3); % initialize edge list [n1, n2, weight]
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for e=1:m
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ind_m1 = find(inc(:,e)==-1);
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ind_p1 = find(inc(:,e)==1);
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if numel(ind_m1)==0 && numel(ind_p1)==1 % undirected, self-loop
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el(e,:) = [ind_p1 ind_p1 1];
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elseif numel(ind_m1)==0 && numel(ind_p1)==2 % undirected
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el(e,:) = [ind_p1(1) ind_p1(2) 1];
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el=[el; ind_p1(2) ind_p1(1) 1];
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elseif numel(ind_m1)==1 && numel(ind_p1)==1 % directed
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el(e,:) = [ind_m1 ind_p1 1];
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end
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end
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