comparison toolboxes/FullBNT-1.0.7/bnt/general/sample_dbn.m @ 0:e9a9cd732c1e tip

first hg version after svn

+function seq = sample_dbn(bnet, varargin)
+% SAMPLE_DBN Generate a random sequence from a DBN.
+% seq = sample_dbn(bnet, ...)
+%
+% seq{i,t} contains the values of the i'th node in the t'th slice.
+%
+% Optional arguments:
+%
+% length - length of sequence  to be generated (can also just use sample_dbn(bnet,T))
+% stop_test - name of a function which is used to decide when to stop;
+%   This will be called as feval(stop_test, seq(:,t))
+%   i.e., stop_test is passed a cell array containing all the nodes in the current slice.   
+% evidence - initial evidence; if evidence{i,t} is non-empty, this node won't be sampled.
+
+args = varargin;
+nargs = length(args);
+
+if (nargs == 1) & ~isstr(args{1})
+  % Old syntax: sample_dbn(bnet, T)
+  T = args{1};
+else
+  % get length
+  T = 1;
+  for i=1:2:nargs
+    switch args{i},
+     case 'length',      T = args{i+1}; 
+     case 'evidence',    T = size(args{i+1}, 2);
+    end
+  end
+end
+
+ss = length(bnet.intra);
+% set default arguments
+seq = cell(ss, T);
+stop_test = [];
+for i=1:2:nargs
+  switch args{i},
+   case 'evidence',    seq = args{i+1}; % initialise observed nodes
+   case 'stop_test',  stop_test = args{i+1};
+  end
+end
+
+t = 1;
+for i=1:ss
+  if ~isempty(stop_test) | isempty(seq{i,t})
+    ps = parents(bnet.dag, i);
+    e = bnet.equiv_class(i,1);
+    pvals = seq(ps);
+    seq{i,t} = sample_node(bnet.CPD{e}, pvals);
+    %fprintf('sample i=%d,t=%d,val=%d,ps\n', i, t, seq(i,t)); pvals(:)'
+  end
+end
+t = 2;
+done = 0;
+while ~done
+  for i=1:ss
+    if ~isempty(stop_test) | isempty(seq{i,t})
+      ps = parents(bnet.dag, i+ss) + (t-2)*ss;
+      e = bnet.equiv_class(i,2);
+      pvals = seq(ps);
+      seq{i,t} = sample_node(bnet.CPD{e}, pvals);
+      %fprintf('sample i=%d,t=%d,val=%d,ps\n', i, t, seq(i,t)); pvals(:)'
+    end
+  end
+  if ~isempty(stop_test)
+    done = feval(stop_test, seq(:,t));
+  else
+    if t==T
+      done = 1;
+    end
+  end
+  t = t + 1;
+end