Package org.apache.commons.rng.sampling.distribution

Class DirichletSampler

java.lang.Object

org.apache.commons.rng.sampling.distribution.DirichletSampler

All Implemented Interfaces:

ObjectSampler<double[]>, SharedStateObjectSampler<double[]>, SharedStateSampler<SharedStateObjectSampler<double[]>>

public abstract class DirichletSampler
extends Object
implements SharedStateObjectSampler<double[]>

Sampling from a Dirichlet distribution.

Sampling uses:

• UniformRandomProvider.nextLong()
• UniformRandomProvider.nextDouble()

Since:

1.4

Method Summary

Modifier and Type	Method	Description
protected abstract int	getK()	Gets the number of categories.
protected abstract double	nextGamma(int category)	Create a gamma sample for the given category.
static DirichletSampler	of(UniformRandomProvider rng, double... alpha)	Creates a new Dirichlet distribution sampler.
double[]	sample()	Create an object sample.
static DirichletSampler	symmetric(UniformRandomProvider rng, int k, double alpha)	Creates a new symmetric Dirichlet distribution sampler using the same concentration parameter for each category.
String	toString()
abstract DirichletSampler	withUniformRandomProvider(UniformRandomProvider rng)	Create a new instance of the sampler with the same underlying state using the given uniform random provider as the source of randomness.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.commons.rng.sampling.ObjectSampler

samples, samples

Method Detail

toString

public String toString()

Overrides:

toString in class Object

sample

public double[] sample()

Description copied from interface: ObjectSampler

Create an object sample.

Specified by:

sample in interface ObjectSampler<double[]>

Returns:

a sample.

getK

protected abstract int getK()

Gets the number of categories.

Returns:

k

nextGamma

protected abstract double nextGamma(int category)

Create a gamma sample for the given category.

Parameters:

category - Category.

Returns:

the sample

withUniformRandomProvider

public abstract DirichletSampler withUniformRandomProvider(UniformRandomProvider rng)

Create a new instance of the sampler with the same underlying state using the given uniform random provider as the source of randomness.

Specified by:

withUniformRandomProvider in interface SharedStateSampler<SharedStateObjectSampler<double[]>>

Parameters:

rng - Generator of uniformly distributed random numbers.

Returns:

the sampler

of

public static DirichletSampler of(UniformRandomProvider rng,
                                  double... alpha)

Creates a new Dirichlet distribution sampler.

Parameters:

rng - Generator of uniformly distributed random numbers.

alpha - Concentration parameters.

Returns:

the sampler

Throws:

IllegalArgumentException - if the number of concentration parameters is less than 2; or if any concentration parameter is not strictly positive.

symmetric

public static DirichletSampler symmetric(UniformRandomProvider rng,
                                         int k,
                                         double alpha)

Creates a new symmetric Dirichlet distribution sampler using the same concentration parameter for each category.

Parameters:

rng - Generator of uniformly distributed random numbers.

k - Number of categories.

alpha - Concentration parameter.

Returns:

the sampler

Throws:

IllegalArgumentException - if the number of categories is less than 2; or if the concentration parameter is not strictly positive.