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