`nltk.NgramAssocMeasures`¶

class nltk.NgramAssocMeasures[source]¶

An abstract class defining a collection of generic association measures. Each public method returns a score, taking the following arguments:

score_fn(count_of_ngram,
         (count_of_n-1gram_1, ..., count_of_n-1gram_j),
         (count_of_n-2gram_1, ..., count_of_n-2gram_k),
         ...,
         (count_of_1gram_1, ..., count_of_1gram_n),
         count_of_total_words)

See BigramAssocMeasures and TrigramAssocMeasures

Inheriting classes should define a property _n, and a method _contingency which calculates contingency values from marginals in order for all association measures defined here to be usable.

Methods¶

`chi_sq`(*marginals)	Scores ngrams using Pearson’s chi-square as in Manning and Schutze 5.3.3.
`jaccard`(*marginals)	Scores ngrams using the Jaccard index.
`likelihood_ratio`(*marginals)	Scores ngrams using likelihood ratios as in Manning and Schutze 5.3.4.
`mi_like`(marginals, *kwargs)	Scores ngrams using a variant of mutual information.
`pmi`(*marginals)	Scores ngrams by pointwise mutual information, as in Manning and Schutze 5.4.
`poisson_stirling`(*marginals)	Scores ngrams using the Poisson-Stirling measure.
`raw_freq`(*marginals)	Scores ngrams by their frequency
`student_t`(*marginals)	Scores ngrams using Student’s t test with independence hypothesis for unigrams, as in Manning and Schutze 5.3.1.