function [engine, loglik] = enter_evidence(engine, evidence, varargin)% ENTER_EVIDENCE Add the specified evidence to the network (hmm)% [engine, loglik] = enter_evidence(engine, evidence, ...)%% evidence{i,t} = [] if if X(i,t) is hidden, and otherwise contains its observed value (scalar or column vector)%% The following optional arguments can be specified in the form of name/value pairs:% [default value in brackets]%% maximize - if 1, does max-product (not yet supported), else sum-product [0]% filter   - if 1, does filtering, else smoothing [0]% oneslice - 1 means only compute marginals on nodes within a single slice [0]%% e.g., engine = enter_evidence(engine, ev, 'maximize', 1)maximize = 0;filter = 0;oneslice = 0;% parse optional paramsargs = varargin;nargs = length(args);if nargs > 0  for i=1:2:nargs    switch args{i},     case 'maximize', maximize = args{i+1};      case 'filter',  filter = args{i+1};      case 'oneslice', oneslice = args{i+1};     otherwise,        error(['invalid argument name ' args{i}]);           end  endend[ss T] = size(evidence);engine.maximize = maximize;engine.evidence = evidence;bnet = bnet_from_engine(engine);engine.node_sizes = repmat(bnet.node_sizes_slice(:), [1 T]);obs_bitv = ~isemptycell(evidence(:));bitv = reshape(obs_bitv, ss, T);for t=1:T  onodes = find(bitv(:,t));  if ~isequal(onodes, bnet.observed(:))    error(['dbn was created assuming observed nodes per slice were '...	   num2str(bnet.observed(:)')  ' but the evidence in slice ' num2str(t) ...	   ' has observed nodes ' num2str(onodes(:)')]);  endendobslik = mk_hmm_obs_lik_matrix(engine, evidence);%[alpha, beta, gamma, loglik, xi] = fwdback(engine.startprob, engine.transprob, obslik, ...[alpha, beta, gamma, loglik, xi] = fwdback_twoslice(engine, engine.startprob,...                                                    engine.transprob, obslik, ...                                                    'maximize', maximize, 'fwd_only', filter, ...                                                    'compute_xi', ~oneslice);engine.one_slice_marginal = gamma; % gamma(:,t) for t=1:Tif ~oneslice  Q = size(gamma,1);  engine.two_slice_marginal = reshape(xi, [Q*Q T-1]); % xi(:,t) for t=1:T-1end