comparison toolboxes/FullBNT-1.0.7/bnt/inference/dynamic/@bk_inf_engine/marginal_nodes.m @ 0:e9a9cd732c1e tip

first hg version after svn

+function marginal = marginal_nodes(engine, nodes, t, fam)
+% MARGINAL_NODES Compute the marginal on the specified query nodes (bk)
+%
+%   marginal = marginal_nodes(engine, i, t)
+% returns Pr(X(i,t) | Y(1:T)), where X(i,t) is the i'th node in the t'th slice.
+% If enter_evidence used filtering instead of smoothing, this will return  Pr(X(i,t) | Y(1:t)).
+%
+%   marginal = marginal_nodes(engine, query, t)
+% returns Pr(X(query(1),t), ... X(query(end),t) | Y(1:T)),
+% where X(q,t) is the q'th node in the t'th slice. If q > ss (slice size), this is equal
+% to X(q mod ss, t+1). That is, 't' specifies the time slice of the earliest node.
+% 'query' cannot span more than 2 time slices.
+% Example:
+% Consider a DBN with 2 nodes per slice.
+% Then t=2, nodes=[1 3] refers to node 1 in slice 2 and node 1 in slice 3.
+
+if nargin < 3, t = 1; end
+if nargin < 4, fam = 0; else fam = 1; end
+
+
+% clpot{t} contains slice t-1 and t
+% Example
+% clpot #: 1    2    3
+% slices:  1  1,2  2,3
+% For filtering, we must take care not to take future evidence into account.
+% For smoothing, clpot{1} does not exist.
+
+bnet = bnet_from_engine(engine);
+ss = length(bnet.intra);
+
+nodes2 = nodes;
+if ~engine.filter
+  if t < engine.T
+    slice = t+1;
+  else % earliest t is T, so all nodes fit in one slice
+    slice = engine.T;
+    nodes2 = nodes + ss;
+  end
+else
+  if t == 1
+   slice = 1;
+  else
+    if all(nodes<=ss)
+      slice = t;
+      nodes2 = nodes + ss;
+    elseif t == engine.T
+      slice = t;
+    else
+      slice = t + 1;
+    end
+  end
+end
+  
+if engine.filter & t==1
+  c = clq_containing_nodes(engine.sub_engine1, nodes2, fam);
+else
+  c = clq_containing_nodes(engine.sub_engine, nodes2, fam);
+end
+assert(c >= 1);
+bigpot = engine.clpot{c, slice};
+
+pot = marginalize_pot(bigpot, nodes2);
+marginal = pot_to_marginal(pot);
+
+% we convert the domain to the unrolled numbering system
+% so that update_ess extracts the right evidence.
+marginal.domain = nodes+(t-1)*ss;