public ICategoricalDistribution jointDistribution(params IProposition[] propositions)
{
ProbabilityTable d = null;
IProposition conjProp = ProbUtil.constructConjunction(propositions);
ISet <IRandomVariable> vars = CollectionFactory.CreateSet <IRandomVariable>(conjProp.getUnboundScope());
if (vars.Size() > 0)
{
IRandomVariable[] distVars = vars.ToArray();
ProbabilityTable ud = new ProbabilityTable(distVars);
object[] values = new object[vars.Size()];
ProbabilityTable.ProbabilityTableIterator di = new ProbabilityTableIterator(conjProp, ud, values, vars);
distribution.iterateOverTable(di);
d = ud;
}
else
{
// No Unbound Variables, therefore just return
// the singular probability related to the proposition.
d = new ProbabilityTable();
d.setValue(0, prior(propositions));
}
return(d);
}
public virtual ICategoricalDistribution jointDistribution(params IProposition[] propositions)
{
ProbabilityTable d = null;
IProposition conjProp = ProbUtil.constructConjunction(propositions);
ISet <IRandomVariable> vars = CollectionFactory.CreateSet <IRandomVariable>(conjProp.getUnboundScope());
if (vars.Size() > 0)
{
IRandomVariable[] distVars = new IRandomVariable[vars.Size()];
int i = 0;
foreach (IRandomVariable rv in vars)
{
distVars[i] = rv;
++i;
}
ProbabilityTable ud = new ProbabilityTable(distVars);
object[] values = new object[vars.Size()];
CategoricalDistributionIterator di = new CategoricalDistributionIteratorJointDistribution(conjProp, vars, ud, values);
IRandomVariable[] X = conjProp.getScope().ToArray();
bayesInference.Ask(X, new AssignmentProposition[0], bayesNet).iterateOver(di);
d = ud;
}
else
{
// No Unbound Variables, therefore just return
// the singular probability related to the proposition.
d = new ProbabilityTable();
d.setValue(0, prior(propositions));
}
return(d);
}
public virtual ICategoricalDistribution posteriorDistribution(IProposition phi, params IProposition[] evidence)
{
IProposition conjEvidence = ProbUtil.constructConjunction(evidence);
// P(A | B) = P(A AND B)/P(B) - (13.3 AIMA3e)
ICategoricalDistribution dAandB = jointDistribution(phi, conjEvidence);
ICategoricalDistribution dEvidence = jointDistribution(conjEvidence);
ICategoricalDistribution rVal = dAandB.divideBy(dEvidence);
// Note: Need to ensure normalize() is called
// in order to handle the case where an approximate
// algorithm is used (i.e. won't evenly divide
// as will have calculated on separate approximate
// runs). However, this should only be done
// if the all of the evidences scope are bound (if not
// you are returning in essence a set of conditional
// distributions, which you do not want normalized).
bool unboundEvidence = false;
foreach (IProposition e in evidence)
{
if (e.getUnboundScope().Size() > 0)
{
unboundEvidence = true;
break;
}
}
if (!unboundEvidence)
{
rVal.normalize();
}
return(rVal);
}
private void sampleFromTransitionModel(int i)
{
// x <- an event initialized with S[i]
IMap <IRandomVariable, object> x = CollectionFactory.CreateInsertionOrderedMap <IRandomVariable, object>();
for (int n = 0; n < S[i].Length; n++)
{
AssignmentProposition x1 = S[i][n];
x.Put(this.dbn.GetX_1_to_X_0().Get(x1.getTermVariable()), x1.getValue());
}
// foreach variable X<sub>1<sub>i</sub></sub> in
// X<sub>1<sub>1</sub></sub>,...,X<sub>1<sub>n<</sub>/sub> do
foreach (IRandomVariable X1_i in dbn.GetX_1_VariablesInTopologicalOrder())
{
// x1[i] <- a random sample from
// <b>P</b>(X<sub>1<sub>i</sub></sub> |
// parents(X<sub>1<sub>i</sub></sub>))
x.Put(X1_i, ProbUtil.randomSample(dbn.GetNode(X1_i), x, randomizer));
}
// S[i] <- sample from <b>P</b>(<b>X</b><sub>1</sub> |
// <b>X</b><sub>0</sub> = S[i])
for (int n = 0; n < S_tp1[i].Length; n++)
{
AssignmentProposition x1 = S_tp1[i][n];
x1.setValue(x.Get(x1.getTermVariable()));
}
}
/**
* Taken {@code weightedSampleWithReplacement} out of {@link ParticleFiltering} and extended by a minimum weight.
* @param samples the samples to be re-sampled.
* @param w the probability distribution on the samples.
* @return the new set of samples.
*/
protected ISet <P> extendedWeightedSampleWithReplacement(ISet <P> samples, double[] w)
{
int i = 0;
for (; i < samples.Size(); ++i)
{
if (w[i] > weightCutOff)
{
break;
}
}
if (i >= samples.Size())
{
return(generateCloud(samples.Size())); /*If all particleCloud are below weightCutOff, generate a new set of samples, as we are lost.*/
}
/*WEIGHTED-SAMPLE-WITH-REPLACEMENT:*/
double[] normalizedW = Util.normalize(w);
ISet <P> newSamples = CollectionFactory.CreateSet <P>();
P[] array = samples.ToArray();
for (i = 0; i < samples.Size(); ++i)
{
int selectedSample = (int)ProbUtil.sample(randomizer.NextDouble(), sampleIndexes, normalizedW);
newSamples.Add((array[selectedSample]).Clone());
}
return(newSamples);
}
// function WEIGHTED-SAMPLE(bn, e) returns an event and a weight
/**
* The WEIGHTED-SAMPLE function in Figure 14.15.
*
* @param e
* observed values for variables E
* @param bn
* a Bayesian network specifying joint distribution
* <b>P</b>(X<sub>1</sub>,...,X<sub>n</sub>)
* @return return <b>x</b>, w - an event with its associated weight.
*/
public Pair <IMap <IRandomVariable, object>, double> weightedSample(IBayesianNetwork bn, AssignmentProposition[] e)
{
// w <- 1;
double w = 1.0;
// <b>x</b> <- an event with n elements initialized from e
IMap <IRandomVariable, object> x = CollectionFactory.CreateInsertionOrderedMap <IRandomVariable, object>();
foreach (AssignmentProposition ap in e)
{
x.Put(ap.getTermVariable(), ap.getValue());
}
// foreach variable X<sub>i</sub> in X<sub>1</sub>,...,X<sub>n</sub> do
foreach (IRandomVariable Xi in bn.GetVariablesInTopologicalOrder())
{
// if X<sub>i</sub> is an evidence variable with value x<sub>i</sub>
// in e
if (x.ContainsKey(Xi))
{
// then w <- w * P(X<sub>i</sub> = x<sub>i</sub> |
// parents(X<sub>i</sub>))
w *= bn.GetNode(Xi)
.GetCPD()
.GetValue(ProbUtil.getEventValuesForXiGivenParents(bn.GetNode(Xi), x));
}
else
{
// else <b>x</b>[i] <- a random sample from
// <b>P</b>(X<sub>i</sub> | parents(X<sub>i</sub>))
x.Put(Xi, ProbUtil.randomSample(bn.GetNode(Xi), x, randomizer));
}
}
// return <b>x</b>, w
return(new Pair <IMap <IRandomVariable, object>, double>(x, w));
}
// function GIBBS-ASK(X, e, bn, N) returns an estimate of <b>P</b>(X|e)
/**
* The GIBBS-ASK algorithm in Figure 14.16. For answering queries given
* evidence in a Bayesian Network.
*
* @param X
* the query variables
* @param e
* observed values for variables E
* @param bn
* a Bayesian network specifying joint distribution
* <b>P</b>(X<sub>1</sub>,...,X<sub>n</sub>)
* @param Nsamples
* the total number of samples to be generated
* @return an estimate of <b>P</b>(X|e)
*/
public CategoricalDistribution gibbsAsk(RandomVariable[] X,
AssignmentProposition[] e, BayesianNetwork bn, int Nsamples)
{
// local variables: <b>N</b>, a vector of counts for each value of X,
// initially zero
double[] N = new double[ProbUtil
.expectedSizeOfCategoricalDistribution(X)];
// Z, the nonevidence variables in bn
Set <RandomVariable> Z = new Set <RandomVariable>(
bn.getVariablesInTopologicalOrder());
foreach (AssignmentProposition ap in e)
{
Z.Remove(ap.getTermVariable());
}
// <b>x</b>, the current state of the network, initially copied from e
Map <RandomVariable, Object> x = new LinkedHashMap <RandomVariable, Object>();
foreach (AssignmentProposition ap in e)
{
x.Add(ap.getTermVariable(), ap.getValue());
}
// initialize <b>x</b> with random values for the variables in Z
foreach (RandomVariable Zi in
Z)
{
x.put(Zi, ProbUtil.randomSample(bn.getNode(Zi), x, randomizer));
}
// for j = 1 to N do
for (int j = 0; j < Nsamples; j++)
{
// for each Z<sub>i</sub> in Z do
foreach (RandomVariable Zi in
Z)
{
// set the value of Z<sub>i</sub> in <b>x</b> by sampling from
// <b>P</b>(Z<sub>i</sub>|mb(Z<sub>i</sub>))
x.put(Zi,
ProbUtil.mbRandomSample(bn.getNode(Zi), x, randomizer));
}
// Note: moving this outside the previous for loop,
// as described in fig 14.6, as will only work
// correctly in the case of a single query variable X.
// However, when multiple query variables, rare events
// will get weighted incorrectly if done above. In case
// of single variable this does not happen as each possible
// value gets * |Z| above, ending up with the same ratios
// when normalized (i.e. its still more efficient to place
// outside the loop).
//
// <b>N</b>[x] <- <b>N</b>[x] + 1
// where x is the value of X in <b>x</b>
N[ProbUtil.indexOf(X, x)] += 1.0;
}
// return NORMALIZE(<b>N</b>)
return(new ProbabilityTable(N, X).normalize());
}
public ICategoricalDistribution posteriorDistribution(IProposition phi,
params IProposition[] evidence)
{
IProposition conjEvidence = ProbUtil.constructConjunction(evidence);
// P(A | B) = P(A AND B)/P(B) - (13.3 AIMA3e)
ICategoricalDistribution dAandB = jointDistribution(phi, conjEvidence);
ICategoricalDistribution dEvidence = jointDistribution(conjEvidence);
return(dAandB.divideBy(dEvidence));
}
public void test_indexesOfValue()
{
RandVar X = new RandVar("X", new BooleanDomain());
RandVar Y = new RandVar("Y", new ArbitraryTokenDomain("A", "B", "C"));
RandVar Z = new RandVar("Z", new BooleanDomain());
// An ordered X,Y,Z enumeration of values should look like:
// 00: true, A, true
// 01: true, A, false
// 02: true, B, true
// 03: true, B, false
// 04: true, C, true
// 05: true, C, false
// 06: false, A, true
// 07: false, A, false
// 08: false, B, true
// 09: false, B, false
// 10: false, C, true
// 11: false, C, false
IRandomVariable[] vars = new IRandomVariable[] { X, Y, Z };
IMap <IRandomVariable, object> even = CollectionFactory.CreateInsertionOrderedMap <IRandomVariable, object>();
even.Put(X, true);
CollectionAssert.AreEqual(new int[] { 0, 1, 2, 3, 4, 5 },
ProbUtil.indexesOfValue(vars, 0, even));
even.Put(X, false);
CollectionAssert.AreEqual(new int[] { 6, 7, 8, 9, 10, 11 },
ProbUtil.indexesOfValue(vars, 0, even));
even.Put(Y, "A");
CollectionAssert.AreEqual(new int[] { 0, 1, 6, 7 },
ProbUtil.indexesOfValue(vars, 1, even));
even.Put(Y, "B");
CollectionAssert.AreEqual(new int[] { 2, 3, 8, 9 },
ProbUtil.indexesOfValue(vars, 1, even));
even.Put(Y, "C");
CollectionAssert.AreEqual(new int[] { 4, 5, 10, 11 },
ProbUtil.indexesOfValue(vars, 1, even));
even.Put(Z, true);
CollectionAssert.AreEqual(new int[] { 0, 2, 4, 6, 8, 10 },
ProbUtil.indexesOfValue(vars, 2, even));
even.Put(Z, false);
CollectionAssert.AreEqual(new int[] { 1, 3, 5, 7, 9, 11 },
ProbUtil.indexesOfValue(vars, 2, even));
}
// function PRIOR-SAMPLE(bn) returns an event sampled from the prior
// specified by bn
/**
* The PRIOR-SAMPLE algorithm in Figure 14.13. A sampling algorithm that
* generates events from a Bayesian network. Each variable is sampled
* according to the conditional distribution given the values already
* sampled for the variable's parents.
*
* @param bn
* a Bayesian network specifying joint distribution
* <b>P</b>(X<sub>1</sub>,...,X<sub>n</sub>)
* @return an event sampled from the prior specified by bn
*/
public Map <RandomVariable, Object> priorSample(BayesianNetwork bn)
{
// x <- an event with n elements
Map <RandomVariable, Object> x = new LinkedHashMap <RandomVariable, Object>();
// foreach variable X<sub>i</sub> in X<sub>1</sub>,...,X<sub>n</sub> do
foreach (RandomVariable Xi in bn.getVariablesInTopologicalOrder())
{
// x[i] <- a random sample from
// <b>P</b>(X<sub>i</sub> | parents(X<sub>i</sub>))
x.Add(Xi, ProbUtil.randomSample(bn.getNode(Xi), x, randomizer));
}
// return x
return(x);
}
// function PRIOR-SAMPLE(bn) returns an event sampled from the prior
// specified by bn
/**
* The PRIOR-SAMPLE algorithm in Figure 14.13. A sampling algorithm that
* generates events from a Bayesian network. Each variable is sampled
* according to the conditional distribution given the values already
* sampled for the variable's parents.
*
* @param bn
* a Bayesian network specifying joint distribution
* <b>P</b>(X<sub>1</sub>,...,X<sub>n</sub>)
* @return an event sampled from the prior specified by bn
*/
public IMap <IRandomVariable, object> priorSample(IBayesianNetwork bn)
{
// x <- an event with n elements
IMap <IRandomVariable, object> x = CollectionFactory.CreateInsertionOrderedMap <IRandomVariable, object>();
// foreach variable X<sub>i</sub> in X<sub>1</sub>,...,X<sub>n</sub> do
foreach (IRandomVariable Xi in bn.GetVariablesInTopologicalOrder())
{
// x[i] <- a random sample from
// <b>P</b>(X<sub>i</sub> | parents(X<sub>i</sub>))
x.Put(Xi, ProbUtil.randomSample(bn.GetNode(Xi), x, randomizer));
}
// return x
return(x);
}
public virtual double posterior(IProposition phi, params IProposition[] evidence)
{
IProposition conjEvidence = ProbUtil.constructConjunction(evidence);
// P(A | B) = P(A AND B)/P(B) - (13.3 AIMA3e)
IProposition aAndB = new ConjunctiveProposition(phi, conjEvidence);
double probabilityOfEvidence = prior(conjEvidence);
if (0 != probabilityOfEvidence)
{
return(prior(aAndB) / probabilityOfEvidence);
}
return(0);
}
// function LIKELIHOOD-WEIGHTING(X, e, bn, N) returns an estimate of
// <b>P</b>(X|e)
/**
* The LIKELIHOOD-WEIGHTING algorithm in Figure 14.15. For answering queries
* given evidence in a Bayesian Network.
*
* @param X
* the query variables
* @param e
* observed values for variables E
* @param bn
* a Bayesian network specifying joint distribution
* <b>P</b>(X<sub>1</sub>,...,X<sub>n</sub>)
* @param N
* the total number of samples to be generated
* @return an estimate of <b>P</b>(X|e)
*/
public ICategoricalDistribution likelihoodWeighting(IRandomVariable[] X, AssignmentProposition[] e, IBayesianNetwork bn, int N)
{
// local variables: W, a vector of weighted counts for each value of X,
// initially zero
double[] W = new double[ProbUtil.expectedSizeOfCategoricalDistribution(X)];
// for j = 1 to N do
for (int j = 0; j < N; j++)
{
// <b>x</b>,w <- WEIGHTED-SAMPLE(bn,e)
Pair <IMap <IRandomVariable, object>, double> x_w = weightedSample(bn, e);
// W[x] <- W[x] + w where x is the value of X in <b>x</b>
W[ProbUtil.indexOf(X, x_w.GetFirst())] += x_w.getSecond();
}
// return NORMALIZE(W)
return(new ProbabilityTable(W, X).normalize());
}
public CategoricalDistribution jointDistribution(
params IProposition[] propositions)
{
ProbabilityTable d = null;
IProposition conjProp = ProbUtil
.constructConjunction(propositions);
LinkedHashSet <RandomVariable> vars = new LinkedHashSet <RandomVariable>(
conjProp.getUnboundScope());
if (vars.Count > 0)
{
RandomVariable[] distVars = new RandomVariable[vars.Count];
vars.CopyTo(distVars);
ProbabilityTable ud = new ProbabilityTable(distVars);
Object[] values = new Object[vars.Count];
//ProbabilityTable.Iterator di = new ProbabilityTable.Iterator() {
// public void iterate(Map<RandomVariable, Object> possibleWorld,
// double probability) {
// if (conjProp.holds(possibleWorld)) {
// int i = 0;
// for (RandomVariable rv : vars) {
// values[i] = possibleWorld.get(rv);
// i++;
// }
// int dIdx = ud.getIndex(values);
// ud.setValue(dIdx, ud.getValues()[dIdx] + probability);
// }
// }
//};
//distribution.iterateOverTable(di);
// TODO:
d = ud;
}
else
{
// No Unbound Variables, therefore just return
// the singular probability related to the proposition.
d = new ProbabilityTable();
d.setValue(0, prior(propositions));
}
return(d);
}
public void test_randomVariableName()
{
string[] names = new[] { "B\ta\t\nf", "B___\n?", null, "a ", " b", "_A1", "Aa \tb c d e", "12asb", "33", "-A\t\b", "-_-" };
foreach (string name in names)
{
try
{
ProbUtil.checkValidRandomVariableName(name);
Assert.Fail("Invalid name string not caught!");
}
catch (Exception)
{ }
}
ProbUtil.checkValidRandomVariableName("A");
ProbUtil.checkValidRandomVariableName("A1");
ProbUtil.checkValidRandomVariableName("A1_2");
ProbUtil.checkValidRandomVariableName("A_a");
}
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]);
}
/**
* The population is re-sampled to generate a new population of N samples.
* Each new sample is selected from the current population; the probability
* that a particular sample is selected is proportional to its weight. The
* new samples are un-weighted.
*
* @param N
* the number of samples
* @param S
* a vector of samples of size N, where each sample is a vector
* of assignment propositions for the X_1 state variables, which
* is intended to represent the sample for time t
* @param W
* a vector of weights of size N
*
* @return a new vector of samples of size N sampled from S based on W
*/
private AssignmentProposition[][] weightedSampleWithReplacement(int N,
AssignmentProposition[][] S, double[] W)
{
AssignmentProposition[][] newS = new AssignmentProposition[N][];
double[] normalizedW = Util.normalize(W);
for (int i = 0; i < N; ++i)
{
newS[i] = new AssignmentProposition[this.dbn.GetX_0().Size()];
int sample = (int)ProbUtil.sample(randomizer.NextDouble(), sampleIndexes, normalizedW);
for (int idx = 0; idx < S_tp1[i].Length; idx++)
{
AssignmentProposition ap = S_tp1[sample][idx];
newS[i][idx] = new AssignmentProposition(ap.getTermVariable(), ap.getValue());
}
}
return(newS);
}
public ICategoricalDistribution forward(ICategoricalDistribution f1_t, ICollection <AssignmentProposition> e_tp1)
{
ICategoricalDistribution s1 = new ProbabilityTable(f1_t.getFor());
// Set up required working variables
IProposition[] props = new IProposition[s1.getFor().Size()];
int i = 0;
foreach (IRandomVariable rv in s1.getFor())
{
props[i] = new RandVar(rv.getName(), rv.getDomain());
++i;
}
IProposition Xtp1 = ProbUtil.constructConjunction(props);
AssignmentProposition[] xt = new AssignmentProposition[tToTm1StateVarMap.Size()];
IMap <IRandomVariable, AssignmentProposition> xtVarAssignMap = CollectionFactory.CreateInsertionOrderedMap <IRandomVariable, AssignmentProposition>();
i = 0;
foreach (IRandomVariable rv in tToTm1StateVarMap.GetKeys())
{
xt[i] = new AssignmentProposition(tToTm1StateVarMap.Get(rv), "<Dummy Value>");
xtVarAssignMap.Put(rv, xt[i]);
++i;
}
// Step 1: Calculate the 1 time step prediction
// ∑<sub>x<sub>t</sub></sub>
CategoricalDistributionIterator if1_t = new CategoricalDistributionIteratorImpl(transitionModel,
xtVarAssignMap, s1, Xtp1, xt);
f1_t.iterateOver(if1_t);
// Step 2: multiply by the probability of the evidence
// and normalize
// <b>P</b>(e<sub>t+1</sub> | X<sub>t+1</sub>)
ICategoricalDistribution s2 = sensorModel.posteriorDistribution(ProbUtil
.constructConjunction(e_tp1.ToArray()), Xtp1);
return(s2.multiplyBy(s1).normalize());
}
// function REJECTION-SAMPLING(X, e, bn, N) returns an estimate of
// <b>P</b>(X|e)
/**
* The REJECTION-SAMPLING algorithm in Figure 14.14. For answering queries
* given evidence in a Bayesian Network.
*
* @param X
* the query variables
* @param e
* observed values for variables E
* @param bn
* a Bayesian network
* @param Nsamples
* the total number of samples to be generated
* @return an estimate of <b>P</b>(X|e)
*/
public ICategoricalDistribution rejectionSampling(IRandomVariable[] X, AssignmentProposition[] e, IBayesianNetwork bn, int Nsamples)
{
// local variables: <b>N</b>, a vector of counts for each value of X,
// initially zero
double[] N = new double[ProbUtil.expectedSizeOfCategoricalDistribution(X)];
// for j = 1 to N do
for (int j = 0; j < Nsamples; j++)
{
// <b>x</b> <- PRIOR-SAMPLE(bn)
IMap <IRandomVariable, object> x = ps.priorSample(bn);
// if <b>x</b> is consistent with e then
if (isConsistent(x, e))
{
// <b>N</b>[x] <- <b>N</b>[x] + 1
// where x is the value of X in <b>x</b>
N[ProbUtil.indexOf(X, x)] += 1.0;
}
}
// return NORMALIZE(<b>N</b>)
return(new ProbabilityTable(N, X).normalize());
}
public ICategoricalDistribution backward(ICategoricalDistribution b_kp2t, ICollection <AssignmentProposition> e_kp1)
{
ICategoricalDistribution b_kp1t = new ProbabilityTable(b_kp2t.getFor());
// Set up required working variables
IProposition[] props = new IProposition[b_kp1t.getFor().Size()];
int i = 0;
foreach (IRandomVariable rv in b_kp1t.getFor())
{
IRandomVariable prv = tToTm1StateVarMap.Get(rv);
props[i] = new RandVar(prv.getName(), prv.getDomain());
++i;
}
IProposition Xk = ProbUtil.constructConjunction(props);
AssignmentProposition[] ax_kp1 = new AssignmentProposition[tToTm1StateVarMap.Size()];
IMap <IRandomVariable, AssignmentProposition> x_kp1VarAssignMap = CollectionFactory.CreateInsertionOrderedMap <IRandomVariable, AssignmentProposition>();
i = 0;
foreach (IRandomVariable rv in b_kp1t.getFor())
{
ax_kp1[i] = new AssignmentProposition(rv, "<Dummy Value>");
x_kp1VarAssignMap.Put(rv, ax_kp1[i]);
++i;
}
IProposition x_kp1 = ProbUtil.constructConjunction(ax_kp1);
props = e_kp1.ToArray();
IProposition pe_kp1 = ProbUtil.constructConjunction(props);
// ∑<sub>x<sub>k+1</sub></sub>
CategoricalDistributionIterator ib_kp2t = new CategoricalDistributionIteratorImpl2(x_kp1VarAssignMap,
sensorModel, transitionModel, b_kp1t, pe_kp1, Xk, x_kp1);
b_kp2t.iterateOver(ib_kp2t);
return(b_kp1t);
}
/**
* The particle filtering algorithm implemented as a recursive update
* operation with state (the set of samples).
*
* @param e
* <b>e</b>, the new incoming evidence
* @return a vector of samples of size N, where each sample is a vector of
* assignment propositions for the X_1 state variables, which is
* intended to represent the generated sample for time t.
*/
public AssignmentProposition[][] particleFiltering(AssignmentProposition[] e)
{
// local variables: W, a vector of weights of size N
double[] W = new double[N];
// for i = 1 to N do
for (int i = 0; i < N; ++i)
{
/* step 1 */
// S[i] <- sample from <b>P</b>(<b>X</b><sub>1</sub> |
// <b>X</b><sub>0</sub> = S[i])
sampleFromTransitionModel(i);
/* step 2 */
// W[i] <- <b>P</b>(<b>e</b> | <b>X</b><sub>1</sub> = S[i])
W[i] = sensorModel.posterior(ProbUtil.constructConjunction(e), S_tp1[i]);
}
/* step 3 */
// S <- WEIGHTED-SAMPLE-WITH-REPLACEMENT(N, S, W)
S = weightedSampleWithReplacement(N, S, W);
// return S
return(S);
}
public Object getSample(double probabilityChoice, params Object[] parentValues)
{
return(ProbUtil.sample(probabilityChoice, on,
getConditioningCase(parentValues).getValues()));
}
public void test_indexOf()
{
RandVar X = new RandVar("X", new BooleanDomain());
RandVar Y = new RandVar("Y", new ArbitraryTokenDomain("A", "B", "C"));
RandVar Z = new RandVar("Z", new BooleanDomain());
// An ordered X,Y,Z enumeration of values should look like:
// 00: true, A, true
// 01: true, A, false
// 02: true, B, true
// 03: true, B, false
// 04: true, C, true
// 05: true, C, false
// 06: false, A, true
// 07: false, A, false
// 08: false, B, true
// 09: false, B, false
// 10: false, C, true
// 11: false, C, false
IRandomVariable[] vars = new IRandomVariable[] { X, Y, Z };
IMap <IRandomVariable, object> even = CollectionFactory.CreateInsertionOrderedMap <IRandomVariable, object>();
even.Put(X, true);
even.Put(Y, "A");
even.Put(Z, true);
Assert.AreEqual(0, ProbUtil.indexOf(vars, even));
even.Put(Z, false);
Assert.AreEqual(1, ProbUtil.indexOf(vars, even));
even.Put(Y, "B");
even.Put(Z, true);
Assert.AreEqual(2, ProbUtil.indexOf(vars, even));
even.Put(Z, false);
Assert.AreEqual(3, ProbUtil.indexOf(vars, even));
even.Put(Y, "C");
even.Put(Z, true);
Assert.AreEqual(4, ProbUtil.indexOf(vars, even));
even.Put(Z, false);
Assert.AreEqual(5, ProbUtil.indexOf(vars, even));
//
even.Put(X, false);
even.Put(Y, "A");
even.Put(Z, true);
Assert.AreEqual(6, ProbUtil.indexOf(vars, even));
even.Put(Z, false);
Assert.AreEqual(7, ProbUtil.indexOf(vars, even));
even.Put(Y, "B");
even.Put(Z, true);
Assert.AreEqual(8, ProbUtil.indexOf(vars, even));
even.Put(Z, false);
Assert.AreEqual(9, ProbUtil.indexOf(vars, even));
even.Put(Y, "C");
even.Put(Z, true);
Assert.AreEqual(10, ProbUtil.indexOf(vars, even));
even.Put(Z, false);
Assert.AreEqual(11, ProbUtil.indexOf(vars, even));
}
public virtual object GetSample(double probabilityChoice, params AssignmentProposition[] parentValues)
{
return(ProbUtil.sample(probabilityChoice, on, GetConditioningCase(parentValues).getValues()));
}
public double prior(params IProposition[] phi)
{
return(probabilityOf(ProbUtil.constructConjunction(phi)));
}
