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function [mi] = calculate_mutual_information_array(data)
% FUNCTION [MI_ARRAY] = CALCULATE_MUTUAL_INFORMATION_ARRAY(DATA)
% calculates the mutual information between all pairs of variables
% Data must be discrete, and take values 1,2,...,size
% data(i,m) is the node i in the case m.
[num_nodes num_examples] = size(data);
node_sizes = max(data');
for i = 1:num_nodes
for ic = 1:node_sizes(i) % I CLASS ic
px(i,ic) = sum(data(i,:)==ic);
for j = 1:num_nodes % J CLASS jc
for jc = 1:node_sizes(j)
pxy(i,ic,j,jc) = sum( (data(i,:)==ic) & (data(j,:)==jc) );
end
mi(i,j) = 0;
end
end
end
for i = 1:num_nodes
for ic = 1:node_sizes(i)
for j = 1:num_nodes
for jc = 1:node_sizes(j)
if( pxy(i,ic,j,jc)~=0 & px(i,ic)~=0 & px(j,jc)~= 0)
mi(i,j) = mi(i,j) + pxy(i,ic,j,jc)*log2( num_examples*pxy(i,ic,j,jc)/(px(i,ic)*px(j,jc)) )/num_examples;
end
end
end
end
end
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