wolffd@0: function CPD = noisyor_CPD(bnet, self, leak_inhibit, inhibit)
wolffd@0: % NOISYOR_CPD Make a noisy-or CPD
wolffd@0: % CPD = NOISYOR_CPD(BNET, NODE_NUM, LEAK_INHIBIT, INHIBIT)
wolffd@0: %
wolffd@0: % A noisy-or node turns on if any of its parents are on, provided they are not inhibited.
wolffd@0: % The prob. that the i'th parent gets inhibited (flipped from 1 to 0) is inhibit(i).
wolffd@0: % The prob that the leak node (a dummy parent that is always on) gets inhibit is leak_inhibit.
wolffd@0: % These params default to random values if omitted.
wolffd@0: %
wolffd@0: % Example: suppose C has parents A and B, and the
wolffd@0: % link of A->C fails with prob pA and the link B->C fails with pB.
wolffd@0: % Then the noisy-OR gate defines the following distribution
wolffd@0: %
wolffd@0: %  A  B  P(C=0)
wolffd@0: %  0  0  1.0
wolffd@0: %  1  0  pA
wolffd@0: %  0  1  pB
wolffd@0: %  1  1  pA * PB
wolffd@0: %
wolffd@0: % Currently, learning is not supported for noisy-or nodes
wolffd@0: % (since the M step is somewhat complicated).
wolffd@0: %
wolffd@0: % For simple generalizations of the noisy-OR model, see e.g.,
wolffd@0: % - Srinivas, "A generalization of the noisy-OR model", UAI 93
wolffd@0: % - Meek and Heckerman, "Learning Causal interaction models", UAI 97.
wolffd@0:   
wolffd@0: 
wolffd@0: 
wolffd@0: if nargin==0
wolffd@0:   % This occurs if we are trying to load an object from a file.
wolffd@0:   CPD = init_fields;
wolffd@0:   CPD = class(CPD, 'noisyor_CPD', discrete_CPD(1, []));
wolffd@0:   return;
wolffd@0: elseif isa(bnet, 'noisyor_CPD')
wolffd@0:   % This might occur if we are copying an object.
wolffd@0:   CPD = bnet;
wolffd@0:   return;
wolffd@0: end
wolffd@0: CPD = init_fields;
wolffd@0: 
wolffd@0: 
wolffd@0: ps = parents(bnet.dag, self);
wolffd@0: fam = [ps self];
wolffd@0: ns = bnet.node_sizes;
wolffd@0: assert(all(ns(fam)==2));
wolffd@0: assert(isempty(myintersect(fam, bnet.cnodes)));
wolffd@0: 
wolffd@0: if nargin < 3, leak_inhibit = rand(1, 1); end
wolffd@0: if nargin < 4, inhibit = rand(1, length(ps)); end
wolffd@0: 
wolffd@0: CPD.self = self;
wolffd@0: CPD.inhibit = inhibit;
wolffd@0: CPD.leak_inhibit = leak_inhibit;
wolffd@0: 
wolffd@0: 
wolffd@0: % For BIC
wolffd@0: CPD.nparams = 0;
wolffd@0: CPD.nsamples = 0;
wolffd@0: 
wolffd@0: CPD.CPT = []; % cached copy, to speed up CPD_to_CPT
wolffd@0: 
wolffd@0: clamped = 1;
wolffd@0: CPD = class(CPD, 'noisyor_CPD', discrete_CPD(clamped, ns([ps self])));
wolffd@0: 
wolffd@0: 
wolffd@0: 
wolffd@0: %%%%%%%%%%%
wolffd@0: 
wolffd@0: function CPD = init_fields()
wolffd@0: % This ensures we define the fields in the same order 
wolffd@0: % no matter whether we load an object from a file,
wolffd@0: % or create it from scratch. (Matlab requires this.)
wolffd@0: 
wolffd@0: CPD.self = [];
wolffd@0: CPD.inhibit = [];
wolffd@0: CPD.leak_inhibit = [];
wolffd@0: CPD.nparams = [];
wolffd@0: CPD.nsamples = [];
wolffd@0: CPD.CPT = [];