diversity_coef_sign.m
3209cc2b0b1dmaster

diversity_coef_sign.m
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			function [Hpos,Hneg] = diversity_coef_sign(W, Ci)
			%DIVERSITY_COEF_SIGN Shannon-entropy based diversity coefficient
			%
			% [Hpos Hneg] = diversity_coef_sign(W,Ci);
			%
			% The Shannon-entropy based diversity coefficient measures the diversity
			% of intermodular connections of individual nodes and ranges from 0 to 1.
			%
			% Inputs: W, undirected connection matrix with positive and
			% negative weights
			%
			% Ci, community affiliation vector
			%
			% Output: Hpos, diversity coefficient based on positive connections
			% Hneg, diversity coefficient based on negative connections
			%
			% References: Shannon CE (1948) Bell Syst Tech J 27, 379-423.
			% Rubinov and Sporns (2011) NeuroImage.
			%
			%
			% 2011-2012, Mika Rubinov, U Cambridge

			% Modification History:
			% Mar 2011: Original
			% Sep 2012: Fixed treatment of nodes with no negative strength
			% (thanks to Alex Fornito and Martin Monti)


			n = length(W); %number of nodes
			m = max(Ci); %number of modules

			Hpos = entropy(W.*(W>0));
			Hneg = entropy(-W.*(W<0));

			function H = entropy(W_)
			S = sum(W_,2); %strength
			Snm = zeros(n,m); %node-to-module degree
			for i = 1:m %loop over modules
			Snm(:,i) = sum(W_(:,Ci==i),2);
			end
			pnm = Snm ./ S(:,ones(1,m));
			pnm(isnan(pnm)) = 0;
			pnm(~pnm) = 1;
			H = -sum(pnm.*log(pnm),2)/log(m);
			end
			end