comparison toolboxes/FullBNT-1.0.7/bnt/inference/dynamic/@ff_inf_engine/Old/marginal_family.m @ 0:e9a9cd732c1e tip

first hg version after svn

+function marginal = marginal_family(engine, i, t)
+% MARGINAL_FAMILY Compute the marginal on the specified family (ff)
+% marginal = marginal_family(engine, i, t)
+
+if nargin < 3, t = 1; end
+
+% The method is similar to the following HMM equation:
+% xi(i,j,t) = normalise( alpha(i,t) * transmat(i,j) * obsmat(j,t+1) * beta(j,t+1) )
+% where xi(i,j,t) = Pr(Q(t)=i, Q(t+1)=j | y(1:T))
+
+bnet = bnet_from_engine(engine);
+
+if myismember(i, engine.onodes)
+  ps = parents(bnet.dag, i);
+  p = ps(1);
+  marginal = pot_to_marginal(engine.marginals{p,t});
+  marginal.domain = [p i];
+  return;
+end
+
+if t==1
+  marginal = pot_to_marginal(engine.marginals{i,t});
+  return;
+end
+
+bnet = bnet_from_engine(engine);
+ss = length(bnet.intra);
+pot = engine.CPDpot{i,t};
+c = engine.obschild(i);
+pot = multiply_by_pot(pot, engine.CPDpot{c,t});
+pot = multiply_by_pot(pot, engine.back{i,t});
+ps = parents(bnet.dag, i+ss);
+for p=ps(:)'
+  pot = multiply_by_pot(pot, engine.fwd{p,t-1});
+end
+marginal = pot_to_marginal(normalize_pot(pot));
+
+