public virtual double prior(params IProposition[] phi)
{
// Calculating the prior, therefore no relevant evidence
// just query over the scope of proposition phi in order
// to get a joint distribution for these
IProposition conjunct = ProbUtil.constructConjunction(phi);
IRandomVariable[] X = conjunct.getScope().ToArray();
ICategoricalDistribution d = bayesInference.Ask(X, new AssignmentProposition[0], bayesNet);
// Then calculate the probability of the propositions phi
// be seeing where they hold.
double[] probSum = new double[1];
CategoricalDistributionIterator di = new CategoricalDistributionIteraorPrior(conjunct, probSum);
d.iterateOver(di);
return(probSum[0]);
}
public void testInferenceOnToothacheCavityCatchNetwork()
{
IBayesianNetwork bn = BayesNetExampleFactory
.constructToothacheCavityCatchNetwork();
ICategoricalDistribution d = bayesInference.Ask(
new IRandomVariable[] { ExampleRV.CAVITY_RV },
new AssignmentProposition[] { }, bn);
// System.Console.WriteLine("P(Cavity)=" + d);
Assert.AreEqual(2, d.getValues().Length);
Assert.AreEqual(0.2, d.getValues()[0],
ProbabilityModelImpl.DEFAULT_ROUNDING_THRESHOLD);
Assert.AreEqual(0.8, d.getValues()[1],
ProbabilityModelImpl.DEFAULT_ROUNDING_THRESHOLD);
// AIMA3e pg. 493
// P(Cavity | toothache) = <0.6, 0.4>
d = bayesInference.Ask(new IRandomVariable[] { ExampleRV.CAVITY_RV },
new AssignmentProposition[] { new AssignmentProposition(
ExampleRV.TOOTHACHE_RV, true) }, bn);
// System.Console.WriteLine("P(Cavity | toothache)=" + d);
Assert.AreEqual(2, d.getValues().Length);
Assert.AreEqual(0.6, d.getValues()[0],
ProbabilityModelImpl.DEFAULT_ROUNDING_THRESHOLD);
Assert.AreEqual(0.4, d.getValues()[1],
ProbabilityModelImpl.DEFAULT_ROUNDING_THRESHOLD);
// AIMA3e pg. 497
// P(Cavity | toothache AND catch) = <0.871, 0.129>
d = bayesInference
.Ask(new IRandomVariable[] { ExampleRV.CAVITY_RV },
new AssignmentProposition[] {
new AssignmentProposition(
ExampleRV.TOOTHACHE_RV, true),
new AssignmentProposition(ExampleRV.CATCH_RV,
true)
}, bn);
// System.Console.WriteLine("P(Cavity | toothache, catch)=" + d);
Assert.AreEqual(2, d.getValues().Length);
Assert.AreEqual(0.8709677419354839, d.getValues()[0],
ProbabilityModelImpl.DEFAULT_ROUNDING_THRESHOLD);
Assert.AreEqual(0.12903225806451615, d.getValues()[1],
ProbabilityModelImpl.DEFAULT_ROUNDING_THRESHOLD);
}
