org.apache.commons.math.distribution
Class AbstractIntegerDistribution

java.lang.Object
  org.apache.commons.math.distribution.AbstractDistribution
      org.apache.commons.math.distribution.AbstractIntegerDistribution

All Implemented Interfaces:

DiscreteDistribution, Distribution, IntegerDistribution, Serializable

Direct Known Subclasses:

BinomialDistributionImpl, HypergeometricDistributionImpl, PoissonDistributionImpl

public abstract class AbstractIntegerDistribution

extends AbstractDistribution

implements IntegerDistribution, Serializable

Base class for integer-valued discrete distributions. Default implementations are provided for some of the methods that do not vary from distribution to distribution.

Version:

$Revision: 1.1 $ $Date: 2004/11/07 03:32:48 $

See Also:

Serialized Form

Field Summary

(package private) static long

serialVersionUID Serializable version identifier

Constructor Summary

protected

AbstractIntegerDistribution() Default constructor.

Method Summary

double	cumulativeProbability(double x) For a random variable X whose values are distributed according to this distribution, this method returns P(X ≤ x).
abstract double	cumulativeProbability(int x) For a random variable X whose values are distributed according to this distribution, this method returns P(X ≤ x).
double	cumulativeProbability(int x0, int x1) For a random variable X whose values are distributed according to this distribution, this method returns P(x0 ≤ X ≤ x1).
protected abstract int	getDomainLowerBound(double p) Access the domain value lower bound, based on p, used to bracket a PDF root.
protected abstract int	getDomainUpperBound(double p) Access the domain value upper bound, based on p, used to bracket a PDF root.
int	inverseCumulativeProbability(double p) For a random variable X whose values are distributed according to this distribution, this method returns the largest x, such that P(X ≤ x) ≤ p.
double	probability(double x) For a random variable X whose values are distributed according to this distribution, this method returns P(X = x).

Methods inherited from class org.apache.commons.math.distribution.AbstractDistribution

cumulativeProbability

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.commons.math.distribution.IntegerDistribution

probability

Methods inherited from interface org.apache.commons.math.distribution.Distribution

cumulativeProbability

Field Detail

serialVersionUID

static final long serialVersionUID

Serializable version identifier

See Also:

Constant Field Values

Constructor Detail

AbstractIntegerDistribution

protected AbstractIntegerDistribution()

Default constructor.

Method Detail

cumulativeProbability

public double cumulativeProbability(double x)
                             throws MathException

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, or CDF, for this distribution.

If x does not represent an integer value, the CDF is evaluated at the greatest integer less than x.

Specified by:

cumulativeProbability in interface Distribution

Parameters:

x - the value at which the distribution function is evaluated.

Returns:

cumulative probability that a random variable with this distribution takes a value less than or equal to x

Throws:

MathException - if the cumulative probability can not be computed due to convergence or other numerical errors.

cumulativeProbability

public abstract double cumulativeProbability(int x)
                                      throws MathException

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 distribution function, or PDF, for this distribution.

Specified by:

cumulativeProbability in interface IntegerDistribution

Parameters:

x - the value at which the PDF is evaluated.

Returns:

PDF for this distribution.

Throws:

MathException - if the cumulative probability can not be computed due to convergence or other numerical errors.

probability

public double probability(double 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, or PMF, for the distribution.

If x does not represent an integer value, 0 is returned.

Specified by:

probability in interface DiscreteDistribution

Parameters:

x - the value at which the probability density function is evaluated

Returns:

the value of the probability density function at x

cumulativeProbability

public double cumulativeProbability(int x0,
                                    int x1)
                             throws MathException

For a random variable X whose values are distributed according to this distribution, this method returns P(x0 ≤ X ≤ x1).

Specified by:

cumulativeProbability in interface IntegerDistribution

Parameters:

x0 - the inclusive, lower bound

x1 - the inclusive, upper bound

Returns:

the cumulative probability.

Throws:

MathException - if the cumulative probability can not be computed due to convergence or other numerical errors.

IllegalArgumentException - if x0 > x1

inverseCumulativeProbability

public int inverseCumulativeProbability(double p)
                                 throws MathException

For a random variable X whose values are distributed according to this distribution, this method returns the largest x, such that P(X ≤ x) ≤ p.

Specified by:

inverseCumulativeProbability in interface IntegerDistribution

Parameters:

p - the desired probability

Returns:

the largest x such that P(X ≤ x) <= p

Throws:

MathException - if the inverse cumulative probability can not be computed due to convergence or other numerical errors.

IllegalArgumentException - if p < 0 or p > 1

getDomainLowerBound

protected abstract int getDomainLowerBound(double p)

Access the domain value lower bound, based on p, used to bracket a PDF root. This method is used by inverseCumulativeProbability(double) to find critical values.

Parameters:

p - the desired probability for the critical value

Returns:

domain value lower bound, i.e. P(X < lower bound) < p

getDomainUpperBound

protected abstract int getDomainUpperBound(double p)

Access the domain value upper bound, based on p, used to bracket a PDF root. This method is used by inverseCumulativeProbability(double) to find critical values.

Parameters:

p - the desired probability for the critical value

Returns:

domain value upper bound, i.e. P(X < upper bound) > p