org.apache.commons.math.distribution
Class AbstractDistribution

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

All Implemented Interfaces:

java.io.Serializable, Distribution

Direct Known Subclasses:

AbstractContinuousDistribution, AbstractIntegerDistribution

public abstract class AbstractDistribution
extends java.lang.Object
implements Distribution, java.io.Serializable

Base class for probability distributions.

Version:

$Id: AbstractDistribution.java 1178295 2011-10-03 04:36:27Z psteitz $

See Also:

Serialized Form

Constructor Summary

protected

AbstractDistribution() Default constructor.

Method Summary

protected abstract double	calculateNumericalMean() Use this method to actually calculate the mean for the specific distribution.
protected abstract double	calculateNumericalVariance() Use this method to actually calculate the variance for the specific distribution.
double	cumulativeProbability(double x0, double x1) For a random variable X whose values are distributed according to this distribution, this method returns P(x0 ≤ X ≤ x1).
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.
boolean	isSupportConnected() Use this method to get information about whether the support is connected, i.e. whether all values between the lower and upper bound of the support is included in the support.
abstract boolean	isSupportLowerBoundInclusive() Use this method to get information about whether the lower bound of the support is inclusive or not.
abstract boolean	isSupportUpperBoundInclusive() Use this method to get information about whether the upper bound of the support is inclusive or not.

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.Distribution

cumulativeProbability

Constructor Detail

AbstractDistribution

protected AbstractDistribution()

Default constructor.

Method Detail

cumulativeProbability

public double cumulativeProbability(double x0,
                                    double x1)

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

The default implementation uses the identity

P(x0 ≤ X ≤ x1) = P(X ≤ x1) - P(X ≤ x0)

Specified by:

cumulativeProbability in interface Distribution

Parameters:

x0 - the (inclusive) lower bound

x1 - the (inclusive) upper bound

Returns:

the probability that a random variable with this distribution will take a value between x0 and x1, including the endpoints.

Throws:

NumberIsTooLargeException - if x0 > x1

calculateNumericalMean

protected abstract double calculateNumericalMean()

Use this method to actually calculate the mean for the specific distribution. Use getNumericalMean() (which implements caching) to actually get the mean.

Returns:

the mean or Double.NaN if it's not defined

getNumericalMean

public double getNumericalMean()

Use this method to get the numerical value of the mean of this distribution.

Specified by:

getNumericalMean in interface Distribution

Returns:

the mean or Double.NaN if it's not defined

calculateNumericalVariance

protected abstract double calculateNumericalVariance()

Use this method to actually calculate the variance for the specific distribution. Use getNumericalVariance() (which implements caching) to actually get the variance.

Returns:

the variance or Double.NaN if it's not defined

getNumericalVariance

public double getNumericalVariance()

Use this method to get the numerical value of the variance of this distribution.

Specified by:

getNumericalVariance in interface Distribution

Returns:

the variance (possibly Double.POSITIVE_INFINITY as for certain cases in TDistributionImpl) or Double.NaN if it's not defined

isSupportLowerBoundInclusive

public abstract boolean isSupportLowerBoundInclusive()

Use this method to get information about whether the lower bound of the support is inclusive or not.

Specified by:

isSupportLowerBoundInclusive in interface Distribution

Returns:

whether the lower bound of the support is inclusive or not

isSupportUpperBoundInclusive

public abstract boolean isSupportUpperBoundInclusive()

Use this method to get information about whether the upper bound of the support is inclusive or not.

Specified by:

isSupportUpperBoundInclusive in interface Distribution

Returns:

whether the upper bound of the support is inclusive or not

isSupportConnected

public boolean isSupportConnected()

Use this method to get information about whether the support is connected, i.e. whether all values between the lower and upper bound of the support is included in the support. For AbstractIntegerDistribution the support is discrete, so if this is true, then the support is {lower bound, lower bound + 1, ..., upper bound}. For AbstractContinuousDistribution the support is continuous, so if this is true, then the support is the interval [lower bound, upper bound] where the limits are inclusive or not according to isSupportLowerBoundInclusive() and isSupportUpperBoundInclusive() (in the example both are true). If both are false, then the support is the interval (lower bound, upper bound)

Specified by:

isSupportConnected in interface Distribution

Returns:

whether the support limits given by subclassed methods are connected or not