35 lines
935 B
Matlab
35 lines
935 B
Matlab
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% The sum of products of degrees across all edges.
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% Source: "Towards a Theory of Scale-Free Graphs: Definition, Properties, and Implications", by Li, Alderson, Doyle, Willinger
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% Note: The total degree is used regardless of whether the graph is directed or not.
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%
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% INPUTs: adjacency matrix, nxn
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% OUTPUTs: s-metric
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%
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% Other routines used: degrees.m
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% GB: last updated, Oct 1 2012
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function s=sMetric(adj)
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[deg,~,~]=degrees(adj);
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edges=find(adj>0);
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s=0;
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for e=1:length(edges)
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[i,j]=ind2sub([length(adj),length(adj)],edges(e));
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s=s+deg(i)*deg(j);
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end
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% ALTERNATIVE ....................
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% [deg,~,~]=degrees(adj);
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% el=adj2edgeL(adj);
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%
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% s=0;
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% for e=1:size(el,1)
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% if el(e,1)==el(e,2)
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% s=s+deg(el(e,1))*deg(el(e,2))*el(e,3)*2; % count self-loops twice
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% else
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% s=s+deg(el(e,1))*deg(el(e,2))*el(e,3); % multiply by the weight for edges with weights
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% end
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% end
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% ................................
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