diff toolboxes/FullBNT-1.0.7/bnt/general/noisyORtoTable.m @ 0:e9a9cd732c1e tip

first hg version after svn

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolboxes/FullBNT-1.0.7/bnt/general/noisyORtoTable.m	Tue Feb 10 15:05:51 2015 +0000
@@ -0,0 +1,32 @@
+function CPT = noisyORtoTable(inhibit, leak_inhibit)
+% NOISYORTOTABLE Convert noisyOR distribution to CPT
+% function CPT = noisyORtoTable(inhibit, leak_inhibit)
+%
+% inhibit(i) = prob i'th parent will be inhibited (flipped from 1 to 0)
+% leak_inhibit - optional suppression of leak
+% CPT(U1,...,Un, X) = Pr(X|U1,...,Un) where the Us are the parents (excluding leak).
+% State 1 = off, 2 = on
+
+if nargin < 2, leak_inhibit = 1; end
+
+q = [leak_inhibit inhibit(:)'];
+
+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       
+
+