org.apache.commons.math.distribution

## Class AbstractContinuousDistribution

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

All Implemented Interfaces:
  Serializable, ContinuousDistribution, Distribution

Direct Known Subclasses:
  BetaDistributionImpl, CauchyDistributionImpl, ChiSquaredDistributionImpl, ExponentialDistributionImpl, FDistributionImpl, GammaDistributionImpl, NormalDistributionImpl, TDistributionImpl, WeibullDistributionImpl

    public abstract class AbstractContinuousDistribution
    extends AbstractDistribution
    implements ContinuousDistribution, Serializable

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

Version:
  $Revision: 1073498 $ $Date: 2011-02-22 21:57:26 +0100 (mar. 22 févr. 2011) $
See Also:
  Serialized Form

### Field Summary

Fields
`protected RandomDataImpl` `randomData` RandomData instance used to generate samples from the distribution
`private static long` `serialVersionUID` Serializable version identifier
`private double` `solverAbsoluteAccuracy` Solver absolute accuracy for inverse cumulative computation

### Constructor Summary

Constructors
`protected` `AbstractContinuousDistribution()` Default constructor.

### Method Summary

Methods
`double` `density(double x)` Return the probability density for a particular point.
`protected abstract double` `getDomainLowerBound(double p)` Access the domain value lower bound, based on `p`, used to bracket a CDF root.
`protected abstract double` `getDomainUpperBound(double p)` Access the domain value upper bound, based on `p`, used to bracket a CDF root.
`protected abstract double` `getInitialDomain(double p)` Access the initial domain value, based on `p`, used to bracket a CDF root.
`protected double` `getSolverAbsoluteAccuracy()` Returns the solver absolute accuracy for inverse cumulative computation.
`double` `inverseCumulativeProbability(double p)` For this distribution, X, this method returns the critical point x, such that P(X < x) = `p`.
`void` `reseedRandomGenerator(long seed)` Reseeds the random generator used to generate samples.
`double` `sample()` Generates a random value sampled from this distribution.
`double[]` `sample(int sampleSize)` Generates a random sample from the distribution.

### 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.Distribution

`cumulativeProbability, cumulativeProbability`

### Field Detail

#### serialVersionUID

    private static final long serialVersionUID

Serializable version identifier

See Also:
  Constant Field Values

#### randomData

    protected final RandomDataImpl randomData

RandomData instance used to generate samples from the distribution

Since:
  2.2

#### solverAbsoluteAccuracy

    private double solverAbsoluteAccuracy

Solver absolute accuracy for inverse cumulative computation

Since:
  2.1

### Constructor Detail

#### AbstractContinuousDistribution

    protected AbstractContinuousDistribution()

Default constructor.

### Method Detail

#### density

    public double density(double x)
                   throws MathRuntimeException

Return the probability density for a particular point.

Parameters:
  `x` - The point at which the density should be computed.
Returns:
  The pdf at point x.
Throws:
  `MathRuntimeException` - if the specialized class hasn't implemented this function
Since:
  2.1

#### inverseCumulativeProbability

    public double inverseCumulativeProbability(double p)
                                        throws MathException

For this distribution, X, this method returns the critical point x, such that P(X < x) = `p`.

Specified by:
  `inverseCumulativeProbability` in interface `ContinuousDistribution`
Parameters:
  `p` - the desired probability
Returns:
  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` is not a valid probability.

#### reseedRandomGenerator

    public void reseedRandomGenerator(long seed)

Reseeds the random generator used to generate samples.

Parameters:
  `seed` - the new seed
Since:
  2.2

#### sample

    public double sample()
                  throws MathException

Generates a random value sampled from this distribution. The default implementation uses the inversion method.

Returns:
  random value
Throws:
  `MathException` - if an error occurs generating the random value
Since:
  2.2

#### sample

    public double[] sample(int sampleSize)
                    throws MathException

Generates a random sample from the distribution. The default implementation generates the sample by calling `sample()` in a loop.

Parameters:
  `sampleSize` - number of random values to generate
Returns:
  an array representing the random sample
Throws:
  `MathException` - if an error occurs generating the sample
  `IllegalArgumentException` - if sampleSize is not positive
Since:
  2.2

#### getInitialDomain

    protected abstract double getInitialDomain(double p)

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

Parameters:
  `p` - the desired probability for the critical value
Returns:
  initial domain value

#### getDomainLowerBound

    protected abstract double getDomainLowerBound(double p)

Access the domain value lower bound, based on `p`, used to bracket a CDF 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 double getDomainUpperBound(double p)

Access the domain value upper bound, based on `p`, used to bracket a CDF 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`

#### getSolverAbsoluteAccuracy

    protected double getSolverAbsoluteAccuracy()

Returns the solver absolute accuracy for inverse cumulative computation.

Returns:
  the maximum absolute error in inverse cumulative probability estimates
Since:
  2.1