Packages

class LDA extends Estimator[LDAModel] with LDAParams with DefaultParamsWritable

Latent Dirichlet Allocation (LDA), a topic model designed for text documents.

Terminology:

  • "term" = "word": an element of the vocabulary
  • "token": instance of a term appearing in a document
  • "topic": multinomial distribution over terms representing some concept
  • "document": one piece of text, corresponding to one row in the input data

Original LDA paper (journal version): Blei, Ng, and Jordan. "Latent Dirichlet Allocation." JMLR, 2003.

Input data (featuresCol): LDA is given a collection of documents as input data, via the featuresCol parameter. Each document is specified as a Vector of length vocabSize, where each entry is the count for the corresponding term (word) in the document. Feature transformers such as org.apache.spark.ml.feature.Tokenizer and org.apache.spark.ml.feature.CountVectorizer can be useful for converting text to word count vectors.

Annotations
@Since( "1.6.0" )
Source
LDA.scala
See also

Latent Dirichlet allocation (Wikipedia)

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  1. LDA
  2. DefaultParamsWritable
  3. MLWritable
  4. LDAParams
  5. HasCheckpointInterval
  6. HasSeed
  7. HasMaxIter
  8. HasFeaturesCol
  9. Estimator
  10. PipelineStage
  11. Logging
  12. Params
  13. Serializable
  14. Serializable
  15. Identifiable
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Parameters

A list of (hyper-)parameter keys this algorithm can take. Users can set and get the parameter values through setters and getters, respectively.

  1. final val checkpointInterval: IntParam

    Param for set checkpoint interval (>= 1) or disable checkpoint (-1).

    Param for set checkpoint interval (>= 1) or disable checkpoint (-1). E.g. 10 means that the cache will get checkpointed every 10 iterations. Note: this setting will be ignored if the checkpoint directory is not set in the SparkContext.

    Definition Classes
    HasCheckpointInterval
  2. final val docConcentration: DoubleArrayParam

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

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

    This is the parameter to a Dirichlet distribution, where larger values mean more smoothing (more regularization).

    If not set by the user, then docConcentration is set automatically. If set to singleton vector [alpha], then alpha is replicated to a vector of length k in fitting. Otherwise, the docConcentration vector must be length k. (default = automatic)

    Optimizer-specific parameter settings:

    • EM
      • Currently only supports symmetric distributions, so all values in the vector should be the same.
      • Values should be greater than 1.0
      • default = uniformly (50 / k) + 1, where 50/k is common in LDA libraries and +1 follows from Asuncion et al. (2009), who recommend a +1 adjustment for EM.
    • Online
      • Values should be greater than or equal to 0
      • default = uniformly (1.0 / k), following the implementation from here.
    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  3. final val featuresCol: Param[String]

    Param for features column name.

    Param for features column name.

    Definition Classes
    HasFeaturesCol
  4. final val k: IntParam

    Param for the number of topics (clusters) to infer.

    Param for the number of topics (clusters) to infer. Must be > 1. Default: 10.

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  5. final val maxIter: IntParam

    Param for maximum number of iterations (>= 0).

    Param for maximum number of iterations (>= 0).

    Definition Classes
    HasMaxIter
  6. final val optimizer: Param[String]

    Optimizer or inference algorithm used to estimate the LDA model.

    Optimizer or inference algorithm used to estimate the LDA model. Currently supported (case-insensitive):

    • "online": Online Variational Bayes (default)
    • "em": Expectation-Maximization

    For details, see the following papers:

    • Online LDA: Hoffman, Blei and Bach. "Online Learning for Latent Dirichlet Allocation." Neural Information Processing Systems, 2010. See here
    • EM: Asuncion et al. "On Smoothing and Inference for Topic Models." Uncertainty in Artificial Intelligence, 2009. See here
    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  7. final val seed: LongParam

    Param for random seed.

    Param for random seed.

    Definition Classes
    HasSeed
  8. final val subsamplingRate: DoubleParam

    For Online optimizer only: optimizer = "online".

    For Online optimizer only: optimizer = "online".

    Fraction of the corpus to be sampled and used in each iteration of mini-batch gradient descent, in range (0, 1].

    Note that this should be adjusted in synch with LDA.maxIter so the entire corpus is used. Specifically, set both so that maxIterations * miniBatchFraction greater than or equal to 1.

    Note: This is the same as the miniBatchFraction parameter in org.apache.spark.mllib.clustering.OnlineLDAOptimizer.

    Default: 0.05, i.e., 5% of total documents.

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  9. final val topicConcentration: DoubleParam

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

    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.

    If not set by the user, then topicConcentration is set automatically. (default = automatic)

    Optimizer-specific parameter settings:

    • EM
      • Value should be greater than 1.0
      • default = 0.1 + 1, where 0.1 gives a small amount of smoothing and +1 follows Asuncion et al. (2009), who recommend a +1 adjustment for EM.
    • Online
      • Value should be greater than or equal to 0
      • default = (1.0 / k), following the implementation from here.
    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  10. final val topicDistributionCol: Param[String]

    Output column with estimates of the topic mixture distribution for each document (often called "theta" in the literature).

    Output column with estimates of the topic mixture distribution for each document (often called "theta" in the literature). Returns a vector of zeros for an empty document.

    This uses a variational approximation following Hoffman et al. (2010), where the approximate distribution is called "gamma." Technically, this method returns this approximation "gamma" for each document.

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )

Members

  1. final def clear(param: Param[_]): LDA.this.type

    Clears the user-supplied value for the input param.

    Clears the user-supplied value for the input param.

    Definition Classes
    Params
  2. def copy(extra: ParamMap): LDA

    Creates a copy of this instance with the same UID and some extra params.

    Creates a copy of this instance with the same UID and some extra params. Subclasses should implement this method and set the return type properly. See defaultCopy().

    Definition Classes
    LDAEstimatorPipelineStageParams
    Annotations
    @Since( "1.6.0" )
  3. def explainParam(param: Param[_]): String

    Explains a param.

    Explains a param.

    param

    input param, must belong to this instance.

    returns

    a string that contains the input param name, doc, and optionally its default value and the user-supplied value

    Definition Classes
    Params
  4. def explainParams(): String

    Explains all params of this instance.

    Explains all params of this instance. See explainParam().

    Definition Classes
    Params
  5. final def extractParamMap(): ParamMap

    extractParamMap with no extra values.

    extractParamMap with no extra values.

    Definition Classes
    Params
  6. final def extractParamMap(extra: ParamMap): ParamMap

    Extracts the embedded default param values and user-supplied values, and then merges them with extra values from input into a flat param map, where the latter value is used if there exist conflicts, i.e., with ordering: default param values less than user-supplied values less than extra.

    Extracts the embedded default param values and user-supplied values, and then merges them with extra values from input into a flat param map, where the latter value is used if there exist conflicts, i.e., with ordering: default param values less than user-supplied values less than extra.

    Definition Classes
    Params
  7. def fit(dataset: Dataset[_]): LDAModel

    Fits a model to the input data.

    Fits a model to the input data.

    Definition Classes
    LDAEstimator
    Annotations
    @Since( "2.0.0" )
  8. def fit(dataset: Dataset[_], paramMaps: Seq[ParamMap]): Seq[LDAModel]

    Fits multiple models to the input data with multiple sets of parameters.

    Fits multiple models to the input data with multiple sets of parameters. The default implementation uses a for loop on each parameter map. Subclasses could override this to optimize multi-model training.

    dataset

    input dataset

    paramMaps

    An array of parameter maps. These values override any specified in this Estimator's embedded ParamMap.

    returns

    fitted models, matching the input parameter maps

    Definition Classes
    Estimator
    Annotations
    @Since( "2.0.0" )
  9. def fit(dataset: Dataset[_], paramMap: ParamMap): LDAModel

    Fits a single model to the input data with provided parameter map.

    Fits a single model to the input data with provided parameter map.

    dataset

    input dataset

    paramMap

    Parameter map. These values override any specified in this Estimator's embedded ParamMap.

    returns

    fitted model

    Definition Classes
    Estimator
    Annotations
    @Since( "2.0.0" )
  10. def fit(dataset: Dataset[_], firstParamPair: ParamPair[_], otherParamPairs: ParamPair[_]*): LDAModel

    Fits a single model to the input data with optional parameters.

    Fits a single model to the input data with optional parameters.

    dataset

    input dataset

    firstParamPair

    the first param pair, overrides embedded params

    otherParamPairs

    other param pairs. These values override any specified in this Estimator's embedded ParamMap.

    returns

    fitted model

    Definition Classes
    Estimator
    Annotations
    @Since( "2.0.0" ) @varargs()
  11. final def get[T](param: Param[T]): Option[T]

    Optionally returns the user-supplied value of a param.

    Optionally returns the user-supplied value of a param.

    Definition Classes
    Params
  12. final def getDefault[T](param: Param[T]): Option[T]

    Gets the default value of a parameter.

    Gets the default value of a parameter.

    Definition Classes
    Params
  13. final def getOrDefault[T](param: Param[T]): T

    Gets the value of a param in the embedded param map or its default value.

    Gets the value of a param in the embedded param map or its default value. Throws an exception if neither is set.

    Definition Classes
    Params
  14. def getParam(paramName: String): Param[Any]

    Gets a param by its name.

    Gets a param by its name.

    Definition Classes
    Params
  15. final def hasDefault[T](param: Param[T]): Boolean

    Tests whether the input param has a default value set.

    Tests whether the input param has a default value set.

    Definition Classes
    Params
  16. def hasParam(paramName: String): Boolean

    Tests whether this instance contains a param with a given name.

    Tests whether this instance contains a param with a given name.

    Definition Classes
    Params
  17. final def isDefined(param: Param[_]): Boolean

    Checks whether a param is explicitly set or has a default value.

    Checks whether a param is explicitly set or has a default value.

    Definition Classes
    Params
  18. final def isSet(param: Param[_]): Boolean

    Checks whether a param is explicitly set.

    Checks whether a param is explicitly set.

    Definition Classes
    Params
  19. lazy val params: Array[Param[_]]

    Returns all params sorted by their names.

    Returns all params sorted by their names. The default implementation uses Java reflection to list all public methods that have no arguments and return Param.

    Definition Classes
    Params
    Note

    Developer should not use this method in constructor because we cannot guarantee that this variable gets initialized before other params.

  20. def save(path: String): Unit

    Saves this ML instance to the input path, a shortcut of write.save(path).

    Saves this ML instance to the input path, a shortcut of write.save(path).

    Definition Classes
    MLWritable
    Annotations
    @Since( "1.6.0" ) @throws( ... )
  21. final def set[T](param: Param[T], value: T): LDA.this.type

    Sets a parameter in the embedded param map.

    Sets a parameter in the embedded param map.

    Definition Classes
    Params
  22. final val supportedOptimizers: Array[String]

    Supported values for Param optimizer.

    Supported values for Param optimizer.

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  23. def toString(): String
    Definition Classes
    Identifiable → AnyRef → Any
  24. def transformSchema(schema: StructType): StructType

    Check transform validity and derive the output schema from the input schema.

    Check transform validity and derive the output schema from the input schema.

    We check validity for interactions between parameters during transformSchema and raise an exception if any parameter value is invalid. Parameter value checks which do not depend on other parameters are handled by Param.validate().

    Typical implementation should first conduct verification on schema change and parameter validity, including complex parameter interaction checks.

    Definition Classes
    LDAPipelineStage
    Annotations
    @Since( "1.6.0" )
  25. val uid: String

    An immutable unique ID for the object and its derivatives.

    An immutable unique ID for the object and its derivatives.

    Definition Classes
    LDAIdentifiable
    Annotations
    @Since( "1.6.0" )
  26. def write: MLWriter

    Returns an MLWriter instance for this ML instance.

    Returns an MLWriter instance for this ML instance.

    Definition Classes
    DefaultParamsWritableMLWritable

Parameter setters

  1. def setCheckpointInterval(value: Int): LDA.this.type

    Annotations
    @Since( "1.6.0" )
  2. def setDocConcentration(value: Double): LDA.this.type

    Annotations
    @Since( "1.6.0" )
  3. def setDocConcentration(value: Array[Double]): LDA.this.type

    Annotations
    @Since( "1.6.0" )
  4. def setFeaturesCol(value: String): LDA.this.type

    The features for LDA should be a Vector representing the word counts in a document.

    The features for LDA should be a Vector representing the word counts in a document. The vector should be of length vocabSize, with counts for each term (word).

    Annotations
    @Since( "1.6.0" )
  5. def setK(value: Int): LDA.this.type

    Annotations
    @Since( "1.6.0" )
  6. def setMaxIter(value: Int): LDA.this.type

    Annotations
    @Since( "1.6.0" )
  7. def setOptimizer(value: String): LDA.this.type

    Annotations
    @Since( "1.6.0" )
  8. def setSeed(value: Long): LDA.this.type

    Annotations
    @Since( "1.6.0" )
  9. def setSubsamplingRate(value: Double): LDA.this.type

    Annotations
    @Since( "1.6.0" )
  10. def setTopicConcentration(value: Double): LDA.this.type

    Annotations
    @Since( "1.6.0" )
  11. def setTopicDistributionCol(value: String): LDA.this.type

    Annotations
    @Since( "1.6.0" )

Parameter getters

  1. final def getCheckpointInterval: Int

    Definition Classes
    HasCheckpointInterval
  2. def getDocConcentration: Array[Double]

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  3. final def getFeaturesCol: String

    Definition Classes
    HasFeaturesCol
  4. def getK: Int

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  5. final def getMaxIter: Int

    Definition Classes
    HasMaxIter
  6. def getOptimizer: String

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  7. final def getSeed: Long

    Definition Classes
    HasSeed
  8. def getSubsamplingRate: Double

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  9. def getTopicConcentration: Double

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  10. def getTopicDistributionCol: String

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )

(expert-only) Parameters

A list of advanced, expert-only (hyper-)parameter keys this algorithm can take. Users can set and get the parameter values through setters and getters, respectively.

  1. final val keepLastCheckpoint: BooleanParam

    For EM optimizer only: optimizer = "em".

    For EM optimizer only: optimizer = "em".

    If using checkpointing, this indicates whether to keep the last checkpoint. If false, then the checkpoint will be deleted. Deleting the checkpoint can cause failures if a data partition is lost, so set this bit with care. Note that checkpoints will be cleaned up via reference counting, regardless.

    See DistributedLDAModel.getCheckpointFiles for getting remaining checkpoints and DistributedLDAModel.deleteCheckpointFiles for removing remaining checkpoints.

    Default: true

    Definition Classes
    LDAParams
    Annotations
    @Since( "2.0.0" )
  2. final val learningDecay: DoubleParam

    For Online optimizer only: optimizer = "online".

    For Online optimizer only: optimizer = "online".

    Learning rate, set as an exponential decay rate. This should be between (0.5, 1.0] to guarantee asymptotic convergence. This is called "kappa" in the Online LDA paper (Hoffman et al., 2010). Default: 0.51, based on Hoffman et al.

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  3. final val learningOffset: DoubleParam

    For Online optimizer only: optimizer = "online".

    For Online optimizer only: optimizer = "online".

    A (positive) learning parameter that downweights early iterations. Larger values make early iterations count less. This is called "tau0" in the Online LDA paper (Hoffman et al., 2010) Default: 1024, following Hoffman et al.

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  4. final val optimizeDocConcentration: BooleanParam

    For Online optimizer only (currently): optimizer = "online".

    For Online optimizer only (currently): optimizer = "online".

    Indicates whether the docConcentration (Dirichlet parameter for document-topic distribution) will be optimized during training. Setting this to true will make the model more expressive and fit the training data better. Default: false

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )

(expert-only) Parameter setters

  1. def setKeepLastCheckpoint(value: Boolean): LDA.this.type

    Annotations
    @Since( "2.0.0" )
  2. def setLearningDecay(value: Double): LDA.this.type

    Annotations
    @Since( "1.6.0" )
  3. def setLearningOffset(value: Double): LDA.this.type

    Annotations
    @Since( "1.6.0" )
  4. def setOptimizeDocConcentration(value: Boolean): LDA.this.type

    Annotations
    @Since( "1.6.0" )

(expert-only) Parameter getters

  1. def getKeepLastCheckpoint: Boolean

    Definition Classes
    LDAParams
    Annotations
    @Since( "2.0.0" )
  2. def getLearningDecay: Double

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  3. def getLearningOffset: Double

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )
  4. def getOptimizeDocConcentration: Boolean

    Definition Classes
    LDAParams
    Annotations
    @Since( "1.6.0" )