comparison toolboxes/FullBNT-1.0.7/bnt/examples/static/learn1.m @ 0:e9a9cd732c1e tip

first hg version after svn

+% Lawn sprinker example from Russell and Norvig p454
+% See www.cs.berkeley.edu/~murphyk/Bayes/usage.html for details.
+
+N = 4; 
+dag = zeros(N,N);
+C = 1; S = 2; R = 3; W = 4;
+dag(C,[R S]) = 1;
+dag(R,W) = 1;
+dag(S,W)=1;
+
+false = 1; true = 2;
+ns = 2*ones(1,N); % binary nodes
+
+bnet = mk_bnet(dag, ns);
+bnet.CPD{C} = tabular_CPD(bnet, C, [0.5 0.5]);
+bnet.CPD{R} = tabular_CPD(bnet, R, [0.8 0.2 0.2 0.8]);
+bnet.CPD{S} = tabular_CPD(bnet, S, [0.5 0.9 0.5 0.1]);
+bnet.CPD{W} = tabular_CPD(bnet, W, [1 0.1 0.1 0.01 0 0.9 0.9 0.99]);
+
+CPT = cell(1,N);
+for i=1:N
+  s=struct(bnet.CPD{i});  % violate object privacy
+  CPT{i}=s.CPT;
+end
+
+% Generate training data
+nsamples = 50;
+samples = cell(N, nsamples);
+for i=1:nsamples
+  samples(:,i) = sample_bnet(bnet);
+end
+data = cell2num(samples);
+
+% Make a tabula rasa
+bnet2 = mk_bnet(dag, ns);
+seed = 0;
+rand('state', seed);
+bnet2.CPD{C} = tabular_CPD(bnet2, C, 'clamped', 1, 'CPT', [0.5 0.5], ...
+			   'prior_type', 'dirichlet', 'dirichlet_weight', 0);
+bnet2.CPD{R} = tabular_CPD(bnet2, R, 'prior_type', 'dirichlet', 'dirichlet_weight', 0);
+bnet2.CPD{S} = tabular_CPD(bnet2, S, 'prior_type', 'dirichlet', 'dirichlet_weight', 0);
+bnet2.CPD{W} = tabular_CPD(bnet2, W, 'prior_type', 'dirichlet', 'dirichlet_weight', 0);
+
+
+% Find MLEs from fully observed data
+bnet4 = learn_params(bnet2, samples);
+
+% Bayesian updating with 0 prior is equivalent to ML estimation
+bnet5 = bayes_update_params(bnet2, samples);
+
+CPT4 = cell(1,N);
+for i=1:N
+  s=struct(bnet4.CPD{i});  % violate object privacy
+  CPT4{i}=s.CPT;
+end
+
+CPT5 = cell(1,N);
+for i=1:N
+  s=struct(bnet5.CPD{i});  % violate object privacy
+  CPT5{i}=s.CPT;
+  assert(approxeq(CPT5{i}, CPT4{i}))
+end
+
+
+if 1
+% Find MLEs from partially observed data
+
+% hide 50% of the nodes
+samplesH = samples;
+hide = rand(N, nsamples) > 0.5;
+[I,J]=find(hide);
+for k=1:length(I)
+  samplesH{I(k), J(k)} = [];
+end
+
+engine = jtree_inf_engine(bnet2);
+max_iter = 5;
+[bnet6, LL] = learn_params_em(engine, samplesH, max_iter);
+
+CPT6 = cell(1,N);
+for i=1:N
+  s=struct(bnet6.CPD{i});  % violate object privacy
+  CPT6{i}=s.CPT;
+end
+
+end