Constructor Detail

• CharacterNgramFeatureFunction

  public CharacterNgramFeatureFunction(CharacterNgramFeatureFunction.Orientation orientation,
                               int start,
                               int end)

• CharacterNgramFeatureFunction

  public CharacterNgramFeatureFunction(CharacterNgramFeatureFunction.Orientation orientation,
                               int start,
                               int end,
                               int minimumValueLength,
                               boolean lowerCase)

• CharacterNgramFeatureFunction

  public CharacterNgramFeatureFunction(String featureName,
                               CharacterNgramFeatureFunction.Orientation orientation,
                               int start,
                               int end)

• CharacterNgramFeatureFunction

  public CharacterNgramFeatureFunction(String featureName,
                               CharacterNgramFeatureFunction.Orientation orientation,
                               int start,
                               int end,
                               int minimumValueLength,
                               boolean lowerCase)

  This feature function serves up character n-grams based on StringValued features. For example, if you wanted trigram suffixes (e.g. 'ion' of 'emotion') for words that are of length 7 or more you could call the constructor with the following: CharacterNGramFeatureFunction(Orientation.RIGHT_TO_LEFT, 0, 3, 7, false)

  Parameters:

  featureName - a user-specified name for the feature function, to be included in all feature names.

  orientation - must be one of LEFT_TO_RIGHT or RIGHT_TO_LEFT. The orientation determines whether index 0 corresponds to the first character of the string value or the last. The orientation does not affect the ordering of the characters in the n-gram which are always returned in left-to-right order.

  start - the start of the n-gram (typically 0 for both orientations)

  end - the end of the n-gram (typically n for both orientations)

  minimumValueLength - This parameter allows you to skip string values that are too short. It must be greater than or equal to end.

  lowerCase - if true than the n-gram used as the feature value will be lowercased.

Method Detail

• apply

  public List<Feature> apply(Feature feature)

  Specified by:

  apply in interface Function<Feature,List<Feature>>

  Returns:

  will return an empty list if the value of the feature is not a StringValue or is not as long as the minimumValueLength.