org.apache.lucene.search.similarities

## Class Lambda

- java.lang.Object
- - org.apache.lucene.search.similarities.Lambda

- Direct Known Subclasses:
    LambdaDF, LambdaTTF

      public abstract class Lambda
      extends Object

  The lambda (λw) parameter in information-based models.
  See Also:
    `IBSimilarity`
  WARNING: This API is experimental and might change in incompatible ways in the next release.

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `Lambda()` Sole constructor.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `abstract Explanation` | `explain(BasicStats stats)` Explains the lambda parameter.
    `abstract float` | `lambda(BasicStats stats)` Computes the lambda parameter.
    `abstract String` | `toString()` Subclasses must override this method to return the code of the lambda formula.

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

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

- - ### Constructor Detail

    - #### Lambda

          public Lambda()

      Sole constructor. (For invocation by subclass constructors, typically implicit.)

  - ### Method Detail

    - #### lambda

          public abstract float lambda(BasicStats stats)

      Computes the lambda parameter.

    - #### explain

          public abstract Explanation explain(BasicStats stats)

      Explains the lambda parameter.

    - #### toString

          public abstract String toString()

      Subclasses must override this method to return the code of the lambda formula. Since the original paper is not very clear on this matter, and also uses the DFR naming scheme incorrectly, the codes here were chosen arbitrarily.
      Overrides:
        `toString` in class `Object`

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