opennlp.tools.ngram

Class NGramUtils

java.lang.Object

opennlp.tools.ngram.NGramUtils

public class NGramUtils
extends Object

Utility class for ngrams. Some methods apply specifically to certain 'n' values, for e.g. tri/bi/uni-grams.

Constructor Summary

Constructors

Constructor and Description
NGramUtils()

Method Summary

Modifier and Type	Method and Description
static double	calculateBigramMLProbability(String x0, String x1, Collection<StringList> set) calculate the probability of a bigram in a vocabulary using maximum likelihood estimation
static double	calculateBigramPriorSmoothingProbability(String x0, String x1, Collection<StringList> set, Double k) calculate the probability of a bigram in a vocabulary using prior Laplace smoothing algorithm
static double	calculateLaplaceSmoothingProbability(StringList ngram, Iterable<StringList> set, Double k) calculate the probability of a ngram in a vocabulary using Laplace smoothing algorithm
static double	calculateMissingNgramProbabilityMass(StringList ngram, Double discount, Iterable<StringList> set) calculate the probability of a ngram in a vocabulary using the missing probability mass algorithm
static double	calculateNgramMLProbability(StringList ngram, Iterable<StringList> set) calculate the probability of a ngram in a vocabulary using maximum likelihood estimation
static double	calculateTrigramLinearInterpolationProbability(String x0, String x1, String x2, Collection<StringList> set, Double lambda1, Double lambda2, Double lambda3) calculate the probability of a trigram in a vocabulary using a linear interpolation algorithm
static double	calculateTrigramMLProbability(String x0, String x1, String x2, Iterable<StringList> set) calculate the probability of a trigram in a vocabulary using maximum likelihood estimation
static double	calculateUnigramMLProbability(String word, Collection<StringList> set) calculate the probability of a unigram in a vocabulary using maximum likelihood estimation
static Collection<StringList>	getNGrams(StringList sequence, int size) get the ngrams of dimension n of a certain input sequence of tokens
static StringList	getNMinusOneTokenFirst(StringList ngram) get the (n-1)th ngram of a given ngram, that is the same ngram except the last word in the ngram
static StringList	getNMinusOneTokenLast(StringList ngram) get the (n-1)th ngram of a given ngram, that is the same ngram except the first word in the ngram

Methods inherited from class java.lang.Object

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

Constructor Detail

NGramUtils

public NGramUtils()

Method Detail

calculateLaplaceSmoothingProbability

public static double calculateLaplaceSmoothingProbability(StringList ngram,
                                                          Iterable<StringList> set,
                                                          Double k)

calculate the probability of a ngram in a vocabulary using Laplace smoothing algorithm

Parameters:

ngram - the ngram to get the probability for

set - the vocabulary

k - the smoothing factor

Returns:

the Laplace smoothing probability

See Also:

Additive Smoothing

calculateUnigramMLProbability

public static double calculateUnigramMLProbability(String word,
                                                   Collection<StringList> set)

calculate the probability of a unigram in a vocabulary using maximum likelihood estimation

Parameters:

word - the only word in the unigram

set - the vocabulary

Returns:

the maximum likelihood probability

calculateBigramMLProbability

public static double calculateBigramMLProbability(String x0,
                                                  String x1,
                                                  Collection<StringList> set)

calculate the probability of a bigram in a vocabulary using maximum likelihood estimation

Parameters:

x0 - first word in the bigram

x1 - second word in the bigram

set - the vocabulary

Returns:

the maximum likelihood probability

calculateTrigramMLProbability

public static double calculateTrigramMLProbability(String x0,
                                                   String x1,
                                                   String x2,
                                                   Iterable<StringList> set)

calculate the probability of a trigram in a vocabulary using maximum likelihood estimation

Parameters:

x0 - first word in the trigram

x1 - second word in the trigram

x2 - third word in the trigram

set - the vocabulary

Returns:

the maximum likelihood probability

calculateNgramMLProbability

public static double calculateNgramMLProbability(StringList ngram,
                                                 Iterable<StringList> set)

calculate the probability of a ngram in a vocabulary using maximum likelihood estimation

Parameters:

ngram - a ngram

set - the vocabulary

Returns:

the maximum likelihood probability

calculateBigramPriorSmoothingProbability

public static double calculateBigramPriorSmoothingProbability(String x0,
                                                              String x1,
                                                              Collection<StringList> set,
                                                              Double k)

calculate the probability of a bigram in a vocabulary using prior Laplace smoothing algorithm

Parameters:

x0 - the first word in the bigram

x1 - the second word in the bigram

set - the vocabulary

k - the smoothing factor

Returns:

the prior Laplace smoothiing probability

calculateTrigramLinearInterpolationProbability

public static double calculateTrigramLinearInterpolationProbability(String x0,
                                                                    String x1,
                                                                    String x2,
                                                                    Collection<StringList> set,
                                                                    Double lambda1,
                                                                    Double lambda2,
                                                                    Double lambda3)

calculate the probability of a trigram in a vocabulary using a linear interpolation algorithm

Parameters:

x0 - the first word in the trigram

x1 - the second word in the trigram

x2 - the third word in the trigram

set - the vocabulary

lambda1 - trigram interpolation factor

lambda2 - bigram interpolation factor

lambda3 - unigram interpolation factor

Returns:

the linear interpolation probability

calculateMissingNgramProbabilityMass

public static double calculateMissingNgramProbabilityMass(StringList ngram,
                                                          Double discount,
                                                          Iterable<StringList> set)

calculate the probability of a ngram in a vocabulary using the missing probability mass algorithm

Parameters:

ngram - the ngram

discount - discount factor

set - the vocabulary

Returns:

the probability

getNMinusOneTokenFirst

public static StringList getNMinusOneTokenFirst(StringList ngram)

get the (n-1)th ngram of a given ngram, that is the same ngram except the last word in the ngram

Parameters:

ngram - a ngram

Returns:

a ngram

getNMinusOneTokenLast

public static StringList getNMinusOneTokenLast(StringList ngram)

get the (n-1)th ngram of a given ngram, that is the same ngram except the first word in the ngram

Parameters:

ngram - a ngram

Returns:

a ngram

getNGrams

public static Collection<StringList> getNGrams(StringList sequence,
                                               int size)

get the ngrams of dimension n of a certain input sequence of tokens

Parameters:

sequence - a sequence of tokens

size - the size of the resulting ngrmams

Returns:

all the possible ngrams of the given size derivable from the input sequence