Mercurial > hg > camir-aes2014
view toolboxes/FullBNT-1.0.7/bnt/CPDs/@noisyor_CPD/CPD_to_CPT.m @ 0:e9a9cd732c1e tip
first hg version after svn
author | wolffd |
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date | Tue, 10 Feb 2015 15:05:51 +0000 |
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function CPT = CPD_to_CPT(CPD) % CPD_TO_CPT Convert the discrete CPD to tabular form (noisyor) % CPT = CPD_to_CPT(CPD) % % CPT(U1,...,Un, X) = Pr(X|U1,...,Un) where the Us are the parents (excluding leak). if ~isempty(CPD.CPT) CPT = CPD.CPT; % remember to flush cache if params change (e.g., during learning) return; end q = [CPD.leak_inhibit CPD.inhibit(:)']; % q(i) is the prob. that the i'th parent will be inhibited (flipped from 1 to 0). % q(1) is the leak inhibition probability, and length(q) = n + 1. if length(q)==1 CPT = [q 1-q]; return; end n = length(q); Bn = ind2subv(2*ones(1,n), 1:(2^n))-1; % all n bit vectors, with the left most column toggling fastest (LSB) CPT = zeros(2^n, 2); % Pr(X=0 | U_1 .. U_n) = prod_{i: U_i = on} q_i = prod_i q_i ^ U_i = exp(u' * log(q_i)) % This method is problematic when q contains zeros Q = repmat(q(:)', 2^n, 1); Q(logical(~Bn)) = 1; CPT(:,1) = prod(Q,2); CPT(:,2) = 1-CPT(:,1); CPT = reshape(CPT(2:2:end), 2*ones(1,n)); % skip cases in which the leak is off CPD.CPT = CPT;