Mercurial > hg > camir-aes2014
annotate 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 |
parents | |
children |
rev | line source |
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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; |