annotate toolboxes/FullBNT-1.0.7/bnt/inference/dynamic/@bk_inf_engine/marginal_nodes.m @ 0:cc4b1211e677 tip

initial commit to HG from Changeset: 646 (e263d8a21543) added further path and more save "camirversion.m"
author Daniel Wolff
date Fri, 19 Aug 2016 13:07:06 +0200
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Daniel@0 1 function marginal = marginal_nodes(engine, nodes, t, fam)
Daniel@0 2 % MARGINAL_NODES Compute the marginal on the specified query nodes (bk)
Daniel@0 3 %
Daniel@0 4 % marginal = marginal_nodes(engine, i, t)
Daniel@0 5 % returns Pr(X(i,t) | Y(1:T)), where X(i,t) is the i'th node in the t'th slice.
Daniel@0 6 % If enter_evidence used filtering instead of smoothing, this will return Pr(X(i,t) | Y(1:t)).
Daniel@0 7 %
Daniel@0 8 % marginal = marginal_nodes(engine, query, t)
Daniel@0 9 % returns Pr(X(query(1),t), ... X(query(end),t) | Y(1:T)),
Daniel@0 10 % where X(q,t) is the q'th node in the t'th slice. If q > ss (slice size), this is equal
Daniel@0 11 % to X(q mod ss, t+1). That is, 't' specifies the time slice of the earliest node.
Daniel@0 12 % 'query' cannot span more than 2 time slices.
Daniel@0 13 % Example:
Daniel@0 14 % Consider a DBN with 2 nodes per slice.
Daniel@0 15 % Then t=2, nodes=[1 3] refers to node 1 in slice 2 and node 1 in slice 3.
Daniel@0 16
Daniel@0 17 if nargin < 3, t = 1; end
Daniel@0 18 if nargin < 4, fam = 0; else fam = 1; end
Daniel@0 19
Daniel@0 20
Daniel@0 21 % clpot{t} contains slice t-1 and t
Daniel@0 22 % Example
Daniel@0 23 % clpot #: 1 2 3
Daniel@0 24 % slices: 1 1,2 2,3
Daniel@0 25 % For filtering, we must take care not to take future evidence into account.
Daniel@0 26 % For smoothing, clpot{1} does not exist.
Daniel@0 27
Daniel@0 28 bnet = bnet_from_engine(engine);
Daniel@0 29 ss = length(bnet.intra);
Daniel@0 30
Daniel@0 31 nodes2 = nodes;
Daniel@0 32 if ~engine.filter
Daniel@0 33 if t < engine.T
Daniel@0 34 slice = t+1;
Daniel@0 35 else % earliest t is T, so all nodes fit in one slice
Daniel@0 36 slice = engine.T;
Daniel@0 37 nodes2 = nodes + ss;
Daniel@0 38 end
Daniel@0 39 else
Daniel@0 40 if t == 1
Daniel@0 41 slice = 1;
Daniel@0 42 else
Daniel@0 43 if all(nodes<=ss)
Daniel@0 44 slice = t;
Daniel@0 45 nodes2 = nodes + ss;
Daniel@0 46 elseif t == engine.T
Daniel@0 47 slice = t;
Daniel@0 48 else
Daniel@0 49 slice = t + 1;
Daniel@0 50 end
Daniel@0 51 end
Daniel@0 52 end
Daniel@0 53
Daniel@0 54 if engine.filter & t==1
Daniel@0 55 c = clq_containing_nodes(engine.sub_engine1, nodes2, fam);
Daniel@0 56 else
Daniel@0 57 c = clq_containing_nodes(engine.sub_engine, nodes2, fam);
Daniel@0 58 end
Daniel@0 59 assert(c >= 1);
Daniel@0 60 bigpot = engine.clpot{c, slice};
Daniel@0 61
Daniel@0 62 pot = marginalize_pot(bigpot, nodes2);
Daniel@0 63 marginal = pot_to_marginal(pot);
Daniel@0 64
Daniel@0 65 % we convert the domain to the unrolled numbering system
Daniel@0 66 % so that update_ess extracts the right evidence.
Daniel@0 67 marginal.domain = nodes+(t-1)*ss;