org.apache.spark.mllib.clustering

Class LDAModel

java.lang.Object

org.apache.spark.mllib.clustering.LDAModel

All Implemented Interfaces:

Saveable

Direct Known Subclasses:

DistributedLDAModel, LocalLDAModel

public abstract class LDAModel
extends java.lang.Object
implements Saveable

:: Experimental ::

Latent Dirichlet Allocation (LDA) model.

This abstraction permits for different underlying representations, including local and distributed data structures.

Method Summary

Methods

Modifier and Type	Method and Description
scala.Tuple2<int[],double[]>[]	describeTopics() Return the topics described by weighted terms.
abstract scala.Tuple2<int[],double[]>[]	describeTopics(int maxTermsPerTopic) Return the topics described by weighted terms.
abstract Vector	docConcentration() Concentration parameter (commonly named "alpha") for the prior placed on documents' distributions over topics ("theta").
protected abstract double	gammaShape() Shape parameter for random initialization of variational parameter gamma.
abstract int	k() Number of topics
abstract double	topicConcentration() Concentration parameter (commonly named "beta" or "eta") for the prior placed on topics' distributions over terms.
abstract Matrix	topicsMatrix() Inferred topics, where each topic is represented by a distribution over terms.
abstract int	vocabSize() Vocabulary size (number of terms or terms in the vocabulary)

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.spark.mllib.util.Saveable

formatVersion, save

Method Detail

k

public abstract int k()

Number of topics

vocabSize

public abstract int vocabSize()

Vocabulary size (number of terms or terms in the vocabulary)

docConcentration

public abstract Vector docConcentration()

Concentration parameter (commonly named "alpha") for the prior placed on documents' distributions over topics ("theta").

This is the parameter to a Dirichlet distribution.

Returns:

(undocumented)

topicConcentration

public abstract double topicConcentration()

Concentration parameter (commonly named "beta" or "eta") for the prior placed on topics' distributions over terms.

This is the parameter to a symmetric Dirichlet distribution.

Note: The topics' distributions over terms are called "beta" in the original LDA paper by Blei et al., but are called "phi" in many later papers such as Asuncion et al., 2009.

Returns:

(undocumented)

gammaShape

protected abstract double gammaShape()

Shape parameter for random initialization of variational parameter gamma. Used for variational inference for perplexity and other test-time computations.

Returns:

(undocumented)

topicsMatrix

public abstract Matrix topicsMatrix()

Inferred topics, where each topic is represented by a distribution over terms. This is a matrix of size vocabSize x k, where each column is a topic. No guarantees are given about the ordering of the topics.

Returns:

(undocumented)

describeTopics

public abstract scala.Tuple2<int[],double[]>[] describeTopics(int maxTermsPerTopic)

Return the topics described by weighted terms.

Parameters:

maxTermsPerTopic - Maximum number of terms to collect for each topic.

Returns:

Array over topics. Each topic is represented as a pair of matching arrays: (term indices, term weights in topic). Each topic's terms are sorted in order of decreasing weight.

describeTopics

public scala.Tuple2<int[],double[]>[] describeTopics()

Return the topics described by weighted terms.

WARNING: If vocabSize and k are large, this can return a large object!

Returns:

Array over topics. Each topic is represented as a pair of matching arrays: (term indices, term weights in topic). Each topic's terms are sorted in order of decreasing weight.