NegLogLikelihood (Apache OpenNLP Tools 2.5.9 API)
Description: declaration: package: opennlp.tools.ml.maxent.quasinewton, class: NegLogLikelihood

# Class NegLogLikelihood

java.lang.Object
opennlp.tools.ml.maxent.quasinewton.NegLogLikelihood

All Implemented Interfaces:
  `Function`

Direct Known Subclasses:
  `ParallelNegLogLikelihood`

public class NegLogLikelihood extends Object implements Function
Evaluates negative log-likelihood and its gradient from `DataIndexer`.

See Also:
  - `Function`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `NegLogLikelihood(DataIndexer indexer)`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `int`
  `getDimension()`
  `double[]`
  `getInitialPoint()`
  `double[]`
  `gradientAt(double[] x)`
  Computes the gradient.
  `double`
  `valueAt(double[] x)`
  Computes the negative log-likelihood.

  ### Methods inherited from class Object

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

- ## Constructor Details

  - ### NegLogLikelihood

    public NegLogLikelihood(DataIndexer indexer)
    Parameters:
      `indexer` - The `DataIndexer` to use as input provider.

- ## Method Details

  - ### getDimension

    public int getDimension()
    Specified by:
      `getDimension` in interface `Function`
    Returns:
      Retrieves the dimension value.

  - ### getInitialPoint

    public double[] getInitialPoint()
    Returns:
      Retrieves the initial point as `double` array.

  - ### valueAt

    public double valueAt(double[] x)
    Computes the negative log-likelihood.
    Specified by:
      `valueAt` in interface `Function`
    Parameters:
      `x` - The input.
    Returns:
      Returns the computed negative log-likelihood.
    Throws:
      `IllegalArgumentException` - Thrown if parameters were invalid.

  - ### gradientAt

    public double[] gradientAt(double[] x)
    Computes the gradient.
    Specified by:
      `gradientAt` in interface `Function`
    Parameters:
      `x` - The input.
    Returns:
      Returns the computed gradient.
    Throws:
      `IllegalArgumentException` - Thrown if parameters were invalid.