camir-aes2014: toolboxes/FullBNT-1.0.7/bnt/CPDs/@noisyor_CPD/CPD_to

first hg version after svn

rev	line source
wolffd@0	1 function CPT = CPD_to_CPT(CPD)
wolffd@0	2 % CPD_TO_CPT Convert the discrete CPD to tabular form (noisyor)
wolffd@0	3 % CPT = CPD_to_CPT(CPD)
wolffd@0	4 %
wolffd@0	5 % CPT(U1,...,Un, X) = Pr(X\|U1,...,Un) where the Us are the parents (excluding leak).
wolffd@0	6
wolffd@0	7 if ~isempty(CPD.CPT)
wolffd@0	8 CPT = CPD.CPT; % remember to flush cache if params change (e.g., during learning)
wolffd@0	9 return;
wolffd@0	10 end
wolffd@0	11
wolffd@0	12 q = [CPD.leak_inhibit CPD.inhibit(:)'];
wolffd@0	13 % q(i) is the prob. that the i'th parent will be inhibited (flipped from 1 to 0).
wolffd@0	14 % q(1) is the leak inhibition probability, and length(q) = n + 1.
wolffd@0	15
wolffd@0	16 if length(q)==1
wolffd@0	17 CPT = [q 1-q];
wolffd@0	18 return;
wolffd@0	19 end
wolffd@0	20
wolffd@0	21 n = length(q);
wolffd@0	22 Bn = ind2subv(2*ones(1,n), 1:(2^n))-1; % all n bit vectors, with the left most column toggling fastest (LSB)
wolffd@0	23 CPT = zeros(2^n, 2);
wolffd@0	24 % 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))
wolffd@0	25 % This method is problematic when q contains zeros
wolffd@0	26
wolffd@0	27 Q = repmat(q(:)', 2^n, 1);
wolffd@0	28 Q(logical(~Bn)) = 1;
wolffd@0	29 CPT(:,1) = prod(Q,2);
wolffd@0	30 CPT(:,2) = 1-CPT(:,1);
wolffd@0	31
wolffd@0	32 CPT = reshape(CPT(2:2:end), 2*ones(1,n)); % skip cases in which the leak is off
wolffd@0	33
wolffd@0	34 CPD.CPT = CPT;

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