Mercurial > hg > camir-aes2014
comparison 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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-1:000000000000 | 0:e9a9cd732c1e |
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1 function CPT = CPD_to_CPT(CPD) | |
2 % CPD_TO_CPT Convert the discrete CPD to tabular form (noisyor) | |
3 % CPT = CPD_to_CPT(CPD) | |
4 % | |
5 % CPT(U1,...,Un, X) = Pr(X|U1,...,Un) where the Us are the parents (excluding leak). | |
6 | |
7 if ~isempty(CPD.CPT) | |
8 CPT = CPD.CPT; % remember to flush cache if params change (e.g., during learning) | |
9 return; | |
10 end | |
11 | |
12 q = [CPD.leak_inhibit CPD.inhibit(:)']; | |
13 % q(i) is the prob. that the i'th parent will be inhibited (flipped from 1 to 0). | |
14 % q(1) is the leak inhibition probability, and length(q) = n + 1. | |
15 | |
16 if length(q)==1 | |
17 CPT = [q 1-q]; | |
18 return; | |
19 end | |
20 | |
21 n = length(q); | |
22 Bn = ind2subv(2*ones(1,n), 1:(2^n))-1; % all n bit vectors, with the left most column toggling fastest (LSB) | |
23 CPT = zeros(2^n, 2); | |
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)) | |
25 % This method is problematic when q contains zeros | |
26 | |
27 Q = repmat(q(:)', 2^n, 1); | |
28 Q(logical(~Bn)) = 1; | |
29 CPT(:,1) = prod(Q,2); | |
30 CPT(:,2) = 1-CPT(:,1); | |
31 | |
32 CPT = reshape(CPT(2:2:end), 2*ones(1,n)); % skip cases in which the leak is off | |
33 | |
34 CPD.CPT = CPT; |