org.apache.lucene.classification

## Class BooleanPerceptronClassifier

- java.lang.Object
- - org.apache.lucene.classification.BooleanPerceptronClassifier

- All Implemented Interfaces:
    Classifier<Boolean>

      public class BooleanPerceptronClassifier
      extends Object
      implements Classifier<Boolean>

  A perceptron (see `http://en.wikipedia.org/wiki/Perceptron`) based `Boolean` `Classifier`. The weights are calculated using `TermsEnum.totalTermFreq()` both on a per field and a per document basis and then a corresponding `FST` is used for class assignment.
  WARNING: This API is experimental and might change in incompatible ways in the next release.

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `BooleanPerceptronClassifier(IndexReader indexReader, Analyzer analyzer, Query query, Integer batchSize, Double threshold, String classFieldName, String textFieldName)` Creates a `BooleanPerceptronClassifier`

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `ClassificationResult<Boolean>` | `assignClass(String text)` Assign a class (with score) to the given text String
    `List<ClassificationResult<Boolean>>` | `getClasses(String text)` Get all the classes (sorted by score, descending) assigned to the given text String.
    `List<ClassificationResult<Boolean>>` | `getClasses(String text, int max)` Get the first `max` classes (sorted by score, descending) assigned to the given text String.

    - ### Methods inherited from class java.lang.Object

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

- - ### Constructor Detail

    - #### BooleanPerceptronClassifier

          public BooleanPerceptronClassifier(IndexReader indexReader,
                                             Analyzer analyzer,
                                             Query query,
                                             Integer batchSize,
                                             Double threshold,
                                             String classFieldName,
                                             String textFieldName)
                                      throws IOException

      Creates a `BooleanPerceptronClassifier`
      Parameters:
        `indexReader` - the reader on the index to be used for classification
        `analyzer` - an `Analyzer` used to analyze unseen text
        `query` - a `Query` to eventually filter the docs used for training the classifier, or `null` if all the indexed docs should be used
        `batchSize` - the size of the batch of docs to use for updating the perceptron weights
        `threshold` - the threshold used for class separation
        `classFieldName` - the name of the field used as the output for the classifier
        `textFieldName` - the name of the field used as input for the classifier
      Throws:
        `IOException` - if the building of the underlying `FST` fails and / or `TermsEnum` for the text field cannot be found

  - ### Method Detail

    - #### assignClass

          public ClassificationResult<Boolean> assignClass(String text)
                                                    throws IOException

      Assign a class (with score) to the given text String
      Specified by:
        `assignClass` in interface `Classifier<Boolean>`
      Parameters:
        `text` - a String containing text to be classified
      Returns:
        a `ClassificationResult` holding assigned class of type `T` and score
      Throws:
        `IOException` - If there is a low-level I/O error.

    - #### getClasses

          public List<ClassificationResult<Boolean>> getClasses(String text)
                                                         throws IOException

      Get all the classes (sorted by score, descending) assigned to the given text String.
      Specified by:
        `getClasses` in interface `Classifier<Boolean>`
      Parameters:
        `text` - a String containing text to be classified
      Returns:
        the whole list of `ClassificationResult`, the classes and scores. Returns `null` if the classifier can't make lists.
      Throws:
        `IOException` - If there is a low-level I/O error.

    - #### getClasses

          public List<ClassificationResult<Boolean>> getClasses(String text,
                                                                int max)
                                                         throws IOException

      Get the first `max` classes (sorted by score, descending) assigned to the given text String.
      Specified by:
        `getClasses` in interface `Classifier<Boolean>`
      Parameters:
        `text` - a String containing text to be classified
        `max` - the number of return list elements
      Returns:
        the whole list of `ClassificationResult`, the classes and scores. Cut for "max" number of elements. Returns `null` if the classifier can't make lists.
      Throws:
        `IOException` - If there is a low-level I/O error.

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