opendial.bn.distribs

Class ConditionalTable

java.lang.Object

opendial.bn.distribs.ConditionalTable

All Implemented Interfaces:

ProbDistribution

public class ConditionalTable
extends java.lang.Object
implements ProbDistribution

Conditional probability distribution represented as a probability table. The table expresses a generic distribution of type P(X|Y1...Yn), where X is called the "head" random variable, and Y1...Yn the conditional random variables.

Constructing a conditional table should be done via its Builder class: builder = new ConditionalTable.Builder("variable name"); builder.addRow(...); table = builder.build();

This class represent a generic conditional distribution in which the distribution for the head variable X can be represented using arbitrary distributions of type IndependentProbDistribution.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ConditionalTable.Builder Builder class for the conditional table.

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.Set<java.lang.String>	conditionalVars
static java.util.logging.Logger	log
protected java.util.HashMap<Assignment,IndependentDistribution>	table

Constructor Summary

Constructors

Constructor and Description
ConditionalTable(java.lang.String headVar) Constructs a new probability table, with no values
ConditionalTable(java.lang.String headVar, java.util.Map<Assignment,IndependentDistribution> distribs) Constructs a new probability table, with the values in distribs

Method Summary

Modifier and Type	Method and Description
void	addDistrib(Assignment condition, IndependentDistribution distrib) Adds a new continuous probability distribution associated with the given conditional assignment
ConditionalTable	copy() Returns a copy of the probability table
boolean	equals(java.lang.Object o) Returns true if the object o is a conditional distribution with the same content
java.util.Set<Assignment>	getConditions() Returns the set of possible conditional assignments in the table.
java.util.Set<java.lang.String>	getInputVariables() Returns the conditional variables of the table
ProbDistribution	getPosterior(Assignment condition) Returns the posterior distribution obtained by integrating the (possibly partial) conditional assignment.
double	getProb(Assignment condition, Value head) Returns the probability of the head assignment given the conditional assignment.
IndependentDistribution	getProbDistrib(Assignment condition) Returns the (unconditional) probability distribution P(X) given the conditional assignment.
java.util.Set<Value>	getValues() Returns all possible values specified in the table.
java.lang.String	getVariable() Returns the name of the random variable
int	hashCode() Returns the hashcode for the table.
void	modifyVariableId(java.lang.String oldVarId, java.lang.String newVarId) Modifies the distribution table by replace the old variable identifier by the new one
boolean	pruneValues(double threshold) Prunes from the table all values whose probability falls below the threshold
Value	sample(Assignment condition) Sample a head assignment from the distribution P(head|condition), given the condition.
java.lang.String	toString() Returns a pretty print of the distribution

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

log

public static final java.util.logging.Logger log

conditionalVars

protected java.util.Set<java.lang.String> conditionalVars

table

protected java.util.HashMap<Assignment,IndependentDistribution> table

Constructor Detail

ConditionalTable

public ConditionalTable(java.lang.String headVar)

Constructs a new probability table, with no values

Parameters:

headVar - the name of the random variable

ConditionalTable

public ConditionalTable(java.lang.String headVar,
                        java.util.Map<Assignment,IndependentDistribution> distribs)

Constructs a new probability table, with the values in distribs

Parameters:

headVar - the name of the random variable

distribs - the distribs (one for each conditional assignment)

Method Detail

modifyVariableId

public void modifyVariableId(java.lang.String oldVarId,
                             java.lang.String newVarId)

Modifies the distribution table by replace the old variable identifier by the new one

Specified by:

modifyVariableId in interface ProbDistribution

Parameters:

oldVarId - the old variable label

newVarId - the new variable label

addDistrib

public void addDistrib(Assignment condition,
                       IndependentDistribution distrib)

Adds a new continuous probability distribution associated with the given conditional assignment

Parameters:

condition - the conditional assignment

distrib - the distribution (in a continuous, function-based representation) @ if distrib relates to a different random variable

pruneValues

public boolean pruneValues(double threshold)

Prunes from the table all values whose probability falls below the threshold

Specified by:

pruneValues in interface ProbDistribution

Parameters:

threshold - the threshold to apply

Returns:

true if at least one value has been removed, false otherwise

getVariable

public java.lang.String getVariable()

Returns the name of the random variable

Specified by:

getVariable in interface ProbDistribution

Returns:

the (head) random variable

sample

public Value sample(Assignment condition)

Sample a head assignment from the distribution P(head|condition), given the condition. If no assignment can be sampled (due to e.g. an ill-formed distribution), returns an empty assignment.

Specified by:

sample in interface ProbDistribution

Parameters:

condition - the condition

Returns:

the sampled assignment the condition

getProb

public double getProb(Assignment condition,
                      Value head)

Returns the probability of the head assignment given the conditional assignment. The method assumes that the posterior distribution has a discrete form.

Specified by:

getProb in interface ProbDistribution

Parameters:

condition - the conditional assignment

head - the head assignment

Returns:

the resulting probability

getProbDistrib

public IndependentDistribution getProbDistrib(Assignment condition)

Returns the (unconditional) probability distribution P(X) given the conditional assignment.

Specified by:

getProbDistrib in interface ProbDistribution

Parameters:

condition - the conditional assignment

Returns:

the corresponding probability distribution

getPosterior

public ProbDistribution getPosterior(Assignment condition)

Returns the posterior distribution obtained by integrating the (possibly partial) conditional assignment.

Specified by:

getPosterior in interface ProbDistribution

Parameters:

condition - the assignment on a subset of the conditional variables

Returns:

the resulting posterior distribution.

getValues

public java.util.Set<Value> getValues()

Returns all possible values specified in the table. The input values are here ignored (for efficiency reasons), so the method simply extracts all possible head rows in the table.

Specified by:

getValues in interface ProbDistribution

Returns:

the possible values for the head variables.

getConditions

public java.util.Set<Assignment> getConditions()

Returns the set of possible conditional assignments in the table.

Returns:

the set of conditional assignments

getInputVariables

public java.util.Set<java.lang.String> getInputVariables()

Returns the conditional variables of the table

Specified by:

getInputVariables in interface ProbDistribution

Returns:

the set of conditional variables

hashCode

public int hashCode()

Returns the hashcode for the table.

Overrides:

hashCode in class java.lang.Object

copy

public ConditionalTable copy()

Returns a copy of the probability table

Specified by:

copy in interface ProbDistribution

Returns:

the copy

toString

public java.lang.String toString()

Returns a pretty print of the distribution

Overrides:

toString in class java.lang.Object

Returns:

the pretty print

equals

public boolean equals(java.lang.Object o)

Returns true if the object o is a conditional distribution with the same content

Overrides:

equals in class java.lang.Object