nltk.TrigramAssocMeasures
¶
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class
nltk.
TrigramAssocMeasures
[source]¶ A collection of trigram association measures. Each association measure is provided as a function with four arguments:
trigram_score_fn(n_iii, (n_iix, n_ixi, n_xii), (n_ixx, n_xix, n_xxi), n_xxx)
The arguments constitute the marginals of a contingency table, counting the occurrences of particular events in a corpus. The letter i in the suffix refers to the appearance of the word in question, while x indicates the appearance of any word. Thus, for example: n_iii counts (w1, w2, w3), i.e. the trigram being scored n_ixx counts (w1, , *) n_xxx counts (, *, *), i.e. any trigram
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. |