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## weka.classifiers.bayes
Class NaiveBayesMultinomial

    java.lang.Object
      weka.classifiers.Classifier
          weka.classifiers.bayes.NaiveBayesMultinomial

All Implemented Interfaces:
  java.io.Serializable, java.lang.Cloneable, OptionHandler, WeightedInstancesHandler

    public class NaiveBayesMultinomial

extends Classifier
implements WeightedInstancesHandler

The core equation for this classifier: P[Ci|D] = (P[D|Ci] x P[Ci]) / P[D] (Bayes rule) where Ci is class i and D is a document

See Also:
  Serialized Form

Constructor Summary
`NaiveBayesMultinomial()`

Method Summary
`void` | `buildClassifier(Instances instances)` Generates the classifier.
`double[]` | `distributionForInstance(Instance instance)` Calculates the class membership probabilities for the given test instance.
`java.lang.String` | `globalInfo()` Returns a string describing this classifier
`double` | `lnFactorial(int n)` Fast computation of ln(n!) for non-negative ints negative ints are passed on to the general gamma-function based version in weka.core.SpecialFunctions if the current n value is higher than any previous one, the cache is extended and filled to cover it the common case is reduced to a simple array lookup
`static void` | `main(java.lang.String[] argv)` Main method for testing this class.
`java.lang.String` | `toString()`

Methods inherited from class weka.classifiers.Classifier
`classifyInstance, debugTipText, forName, getDebug, getOptions, listOptions, makeCopies, makeCopy, setDebug, setOptions`

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Constructor Detail

### NaiveBayesMultinomial

    public NaiveBayesMultinomial()

Method Detail

### globalInfo

    public java.lang.String globalInfo()

  Returns a string describing this classifier

  Returns:
    a description of the classifier suitable for displaying in the explorer/experimenter gui

### buildClassifier

    public void buildClassifier(Instances instances)
                         throws java.lang.Exception

  Generates the classifier.

  Specified by:
    `buildClassifier` in class `Classifier`
  Parameters:
    `instances` - set of instances serving as training data
  Throws:
    `java.lang.Exception` - if the classifier has not been generated successfully

### distributionForInstance

    public double[] distributionForInstance(Instance instance)
                                     throws java.lang.Exception

  Calculates the class membership probabilities for the given test instance.

  Overrides:
    `distributionForInstance` in class `Classifier`
  Parameters:
    `instance` - the instance to be classified
  Returns:
    predicted class probability distribution
  Throws:
    `java.lang.Exception` - if there is a problem generating the prediction

### lnFactorial

    public double lnFactorial(int n)

  Fast computation of ln(n!) for non-negative ints negative ints are passed on to the general gamma-function based version in weka.core.SpecialFunctions if the current n value is higher than any previous one, the cache is extended and filled to cover it the common case is reduced to a simple array lookup

  Parameters:
    `n` - the integer
  Returns:
    ln(n!)

### toString

    public java.lang.String toString()

  Overrides:
    `toString` in class `java.lang.Object`

### main

    public static void main(java.lang.String[] argv)

  Main method for testing this class.

  Parameters:
    `argv` - the options

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