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1 function [engine, loglik] = enter_evidence(engine, evidence, varargin)
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2 % ENTER_EVIDENCE Add the specified evidence to the network (hmm)
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3 % [engine, loglik] = enter_evidence(engine, evidence, ...)
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4 %
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5 % evidence{i,t} = [] if if X(i,t) is hidden, and otherwise contains its observed value (scalar or column vector)
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6 %
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7 % The following optional arguments can be specified in the form of name/value pairs:
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8 % [default value in brackets]
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9 %
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10 % maximize - if 1, does max-product (not yet supported), else sum-product [0]
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11 % filter - if 1, does filtering, else smoothing [0]
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12 % oneslice - 1 means only compute marginals on nodes within a single slice [0]
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13 %
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14 % e.g., engine = enter_evidence(engine, ev, 'maximize', 1)
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15
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16 maximize = 0;
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17 filter = 0;
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18 oneslice = 0;
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19
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20 % parse optional params
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21 args = varargin;
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22 nargs = length(args);
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23 if nargs > 0
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24 for i=1:2:nargs
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25 switch args{i},
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26 case 'maximize', maximize = args{i+1};
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27 case 'filter', filter = args{i+1};
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28 case 'oneslice', oneslice = args{i+1};
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29 otherwise,
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30 error(['invalid argument name ' args{i}]);
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31 end
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32 end
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33 end
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34
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35 [ss T] = size(evidence);
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36 engine.maximize = maximize;
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37 engine.evidence = evidence;
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38 bnet = bnet_from_engine(engine);
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39 engine.node_sizes = repmat(bnet.node_sizes_slice(:), [1 T]);
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40
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41 obs_bitv = ~isemptycell(evidence(:));
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42 bitv = reshape(obs_bitv, ss, T);
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43 for t=1:T
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44 onodes = find(bitv(:,t));
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45 if ~isequal(onodes, bnet.observed(:))
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46 error(['dbn was created assuming observed nodes per slice were '...
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47 num2str(bnet.observed(:)') ' but the evidence in slice ' num2str(t) ...
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48 ' has observed nodes ' num2str(onodes(:)')]);
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49 end
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50 end
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51
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52 obslik = mk_hmm_obs_lik_matrix(engine, evidence);
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53
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54 %[alpha, beta, gamma, loglik, xi] = fwdback(engine.startprob, engine.transprob, obslik, ...
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55 [alpha, beta, gamma, loglik, xi] = fwdback_twoslice(engine, engine.startprob,...
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56 engine.transprob, obslik, ...
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57 'maximize', maximize, 'fwd_only', filter, ...
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58 'compute_xi', ~oneslice);
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59
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60 engine.one_slice_marginal = gamma; % gamma(:,t) for t=1:T
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61 if ~oneslice
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62 Q = size(gamma,1);
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63 engine.two_slice_marginal = reshape(xi, [Q*Q T-1]); % xi(:,t) for t=1:T-1
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64 end
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