bnt_1 一个用于贝叶斯网络的matlab的工具

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;

 

node_sizes = 2*ones(1,N);

%node_sizes = [ 4 2 3 5];

 

%建立有向无环图

onodes = [];

bNet = mk_bnet( dag, node_sizes );

 

%建立条件概率表

bNet.CPD{C} = tabular_CPD( bNet, C, 'CPT', [0.5 0.5] );

bNet.CPD{R} = tabular_CPD( bNet, R,  'CPT',[0.8 0.2 0.2 0.8 ] );

bNet.CPD{S} = tabular_CPD( bNet, S,  'CPT', [0.5 0.9 0.5 0.1] );

bNet.CPD{W} = tabular_CPD( bNet, W, 'CPT', [1 0.1 0.1 0.01 0 0.9 0.9 0.99 ] );

   

 

 

%用于推断

engine = jtree_inf_engine( bNet);

 

evidence = cell( 1,N );

evidence{W} = 2;

 

%添加证据

[engine, loglik] = enter_evidence( engine, evidence );

marg = marginal_nodes( engine, S );

p = marg.T(2);

 

%添加下雨的证据

evidence{R} = 2;

[ engine, loglik ] = enter_evidence( engine, evidence );

marg = marginal_nodes( engine, S );

p = marg.T(2);

 

bar( marg.T );

 

 

% Joint distributions

evidence = cell(1,N);

[engine, ll] = enter_evidence(engine, evidence);

m = marginal_nodes(engine, [S R W]);

m.T