comparison toolboxes/FullBNT-1.0.7/bnt/examples/dynamic/HHMM/Mgram/mgram1.m @ 0:e9a9cd732c1e tip

first hg version after svn

+% a multigram is a degenerate 2HHMM where the bottom level HMMs emit deterministic strings
+% and the the top level abstract states are independent of each other
+% cf. HSMM/test_mgram2 
+
+words = {'the', 't', 'h', 'e'};
+data = 'the';
+nwords = length(words);
+word_len = zeros(1, nwords);
+word_prob = normalise(ones(1,nwords));
+word_logprob = log(word_prob);
+for wi=1:nwords
+  word_len(wi)=length(words{wi});
+end
+D = max(word_len);
+
+alphasize = 26;
+data = letter2num(data);
+T = length(data);
+
+% node numbers
+W = 1; % top level state = word id
+L = 2; % bottom level state = letter position within word
+F = 3;
+O = 4;
+
+ss = 4;
+intra = zeros(ss,ss);
+intra(W,[F L O])=1;
+intra(L,[O F])=1;
+
+inter = zeros(ss,ss);
+inter(W,W)=1;
+inter(L,L)=1;
+inter(F,[W L])=1;
+
+% node sizes
+ns = zeros(1,ss);
+ns(W) = nwords;
+ns(L) = D;
+ns(F) = 2;
+ns(O) = alphasize;
+
+
+% Make the DBN
+bnet = mk_dbn(intra, inter, ns, 'observed', O);
+eclass = bnet.equiv_class;
+
+
+
+% uniform start distrib over words, uniform trans mat
+Wstart = normalise(ones(1,nwords));
+Wtrans = mk_stochastic(ones(nwords,nwords));
+
+% always start in state 1 for each bottom level HMM
+delta1_start = zeros(1, D);
+delta1_start(1) = 1;
+Lstart = repmat(delta1_start, nwords, 1);
+LRtrans = mk_leftright_transmat(D, 0); % 0 self loop prob
+Ltrans = repmat(LRtrans, [1 1 nwords]);
+
+% Finish in the last letter of each word
+Fprob = zeros(nwords, D, 2);
+Fprob(:,:,1)=1;
+for i=1:nwords
+  Fprob(i,length(words{i}),2)=1;
+  Fprob(i,length(words{i}),1)=0;
+end
+
+% Each state uniquely emits a letter
+Oprob = zeros(nwords, D, alphasize);
+for i=1:nwords
+  for l=1:length(words{i})
+    a = double(words{i}(l))-96;
+    Oprob(i,l,a)=1;
+  end
+end
+
+
+% Define CPDs for slice 
+bnet.CPD{eclass(W,1)} = tabular_CPD(bnet, W, 'CPT', Wstart);
+bnet.CPD{eclass(L,1)} = tabular_CPD(bnet, L, 'CPT', Lstart);
+bnet.CPD{eclass(F,1)} = tabular_CPD(bnet, F, 'CPT', Fprob);
+bnet.CPD{eclass(O,1)} = tabular_CPD(bnet, O, 'CPT', Oprob);
+
+% Define CPDs for slice 2
+bnet.CPD{eclass(W,2)} = hhmmQ_CPD(bnet, W+ss, 'Fbelow', F, 'startprob', Wstart,  'transprob', Wtrans);
+bnet.CPD{eclass(L,2)} = hhmmQ_CPD(bnet, L+ss, 'Fself', F, 'Qps', W+ss, 'startprob', Lstart, 'transprob', Ltrans);
+
+evidence = cell(ss,T);
+evidence{W,1}=1;
+sample = cell2num(sample_dbn(bnet, 'length', T, 'evidence', evidence));
+str = lower(sample(4,:))
+
+engine = jtree_dbn_inf_engine(bnet);
+evidence = cell(ss,T);
+evidence(O,:) = num2cell(data);
+[engine, ll_dbn] = enter_evidence(engine, evidence);
+
+gamma = zeros(nwords, T);
+for t=1:T
+  m = marginal_nodes(engine, [W F], t);
+  gamma(:,t) = m.T(:,2);
+end
+gamma
+
+xidbn = zeros(nwords, nwords);
+for t=1:T-1
+  m = marginal_nodes(engine, [W F W+ss], t);
+  xidbn = xidbn + squeeze(m.T(:,2,:));
+end
+
+% thee
+% xidbn(1,4)  = 0.9412  the->e
+% (2,3)=0.0588 t->h
+% (3,4)=0.0588 h-e
+% (4,4)=0.0588 e-e