org.apache.commons.math3.distribution
Class EnumeratedIntegerDistribution

java.lang.Object
  extended by org.apache.commons.math3.distribution.AbstractIntegerDistribution
      extended by org.apache.commons.math3.distribution.EnumeratedIntegerDistribution
All Implemented Interfaces:
Serializable, IntegerDistribution

public class EnumeratedIntegerDistribution
extends AbstractIntegerDistribution

Implementation of an integer-valued EnumeratedDistribution.

Values with zero-probability are allowed but they do not extend the support.
Duplicate values are allowed. Probabilities of duplicate values are combined when computing cumulative probabilities and statistics.

Since:
3.2
Version:
$Id: EnumeratedIntegerDistribution.html 860130 2013-04-27 21:11:39Z luc $
See Also:
Serialized Form

Field Summary
protected  EnumeratedDistribution<Integer> innerDistribution
          EnumeratedDistribution instance (using the Integer wrapper) used to generate the pmf.
 
Fields inherited from class org.apache.commons.math3.distribution.AbstractIntegerDistribution
random, randomData
 
Constructor Summary
EnumeratedIntegerDistribution(int[] singletons, double[] probabilities)
          Create a discrete distribution using the given probability mass function definition.
EnumeratedIntegerDistribution(RandomGenerator rng, int[] singletons, double[] probabilities)
          Create a discrete distribution using the given random number generator and probability mass function definition.
 
Method Summary
 double cumulativeProbability(int x)
          For a random variable X whose values are distributed according to this distribution, this method returns P(X <= x).
 double getNumericalMean()
          Use this method to get the numerical value of the mean of this distribution.
 double getNumericalVariance()
          Use this method to get the numerical value of the variance of this distribution.
 int getSupportLowerBound()
          Access the lower bound of the support.
 int getSupportUpperBound()
          Access the upper bound of the support.
 boolean isSupportConnected()
          Use this method to get information about whether the support is connected, i.e. whether all integers between the lower and upper bound of the support are included in the support.
 double probability(int x)
          For a random variable X whose values are distributed according to this distribution, this method returns P(X = x).
 int sample()
          Generate a random value sampled from this distribution.
 
Methods inherited from class org.apache.commons.math3.distribution.AbstractIntegerDistribution
cumulativeProbability, inverseCumulativeProbability, reseedRandomGenerator, sample, solveInverseCumulativeProbability
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

innerDistribution

protected final EnumeratedDistribution<Integer> innerDistribution
EnumeratedDistribution instance (using the Integer wrapper) used to generate the pmf.

Constructor Detail

EnumeratedIntegerDistribution

public EnumeratedIntegerDistribution(int[] singletons,
                                     double[] probabilities)
                              throws DimensionMismatchException,
                                     NotPositiveException,
                                     MathArithmeticException,
                                     NotFiniteNumberException,
                                     NotANumberException
Create a discrete distribution using the given probability mass function definition.

Parameters:
singletons - array of random variable values.
probabilities - array of probabilities.
Throws:
DimensionMismatchException - if singletons.length != probabilities.length
NotPositiveException - if any of the probabilities are negative.
NotFiniteNumberException - if any of the probabilities are infinite.
NotANumberException - if any of the probabilities are NaN.
MathArithmeticException - all of the probabilities are 0.

EnumeratedIntegerDistribution

public EnumeratedIntegerDistribution(RandomGenerator rng,
                                     int[] singletons,
                                     double[] probabilities)
                              throws DimensionMismatchException,
                                     NotPositiveException,
                                     MathArithmeticException,
                                     NotFiniteNumberException,
                                     NotANumberException
Create a discrete distribution using the given random number generator and probability mass function definition.

Parameters:
rng - random number generator.
singletons - array of random variable values.
probabilities - array of probabilities.
Throws:
DimensionMismatchException - if singletons.length != probabilities.length
NotPositiveException - if any of the probabilities are negative.
NotFiniteNumberException - if any of the probabilities are infinite.
NotANumberException - if any of the probabilities are NaN.
MathArithmeticException - all of the probabilities are 0.
Method Detail

probability

public double probability(int x)
For a random variable X whose values are distributed according to this distribution, this method returns P(X = x). In other words, this method represents the probability mass function (PMF) for the distribution.

Parameters:
x - the point at which the PMF is evaluated
Returns:
the value of the probability mass function at x

cumulativeProbability

public double cumulativeProbability(int x)
For a random variable X whose values are distributed according to this distribution, this method returns P(X <= x). In other words, this method represents the (cumulative) distribution function (CDF) for this distribution.

Parameters:
x - the point at which the CDF is evaluated
Returns:
the probability that a random variable with this distribution takes a value less than or equal to x

getNumericalMean

public double getNumericalMean()
Use this method to get the numerical value of the mean of this distribution.

Returns:
sum(singletons[i] * probabilities[i])

getNumericalVariance

public double getNumericalVariance()
Use this method to get the numerical value of the variance of this distribution.

Returns:
sum((singletons[i] - mean) ^ 2 * probabilities[i])

getSupportLowerBound

public int getSupportLowerBound()
Access the lower bound of the support. This method must return the same value as inverseCumulativeProbability(0). In other words, this method must return

inf {x in Z | P(X <= x) > 0}.

Returns the lowest value with non-zero probability.

Returns:
the lowest value with non-zero probability.

getSupportUpperBound

public int getSupportUpperBound()
Access the upper bound of the support. This method must return the same value as inverseCumulativeProbability(1). In other words, this method must return

inf {x in R | P(X <= x) = 1}.

Returns the highest value with non-zero probability.

Returns:
the highest value with non-zero probability.

isSupportConnected

public boolean isSupportConnected()
Use this method to get information about whether the support is connected, i.e. whether all integers between the lower and upper bound of the support are included in the support. The support of this distribution is connected.

Returns:
true

sample

public int sample()
Generate a random value sampled from this distribution. The default implementation uses the inversion method.

Specified by:
sample in interface IntegerDistribution
Overrides:
sample in class AbstractIntegerDistribution
Returns:
a random value


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