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  2. tf–idf - Wikipedia

    en.wikipedia.org/wiki/Tf–idf

    The tf–idf is the product of two statistics, term frequency and inverse document frequency. There are various ways for determining the exact values of both statistics. A formula that aims to define the importance of a keyword or phrase within a document or a web page.

  3. Letter frequency - Wikipedia

    en.wikipedia.org/wiki/Letter_frequency

    The California Job Case was a compartmentalized box for printing in the 19th century, sizes corresponding to the commonality of letters. The frequency of letters in text has been studied for use in cryptanalysis, and frequency analysis in particular, dating back to the Arab mathematician al-Kindi (c. AD 801–873 ), who formally developed the method (the ciphers breakable by this technique go ...

  4. Okapi BM25 - Wikipedia

    en.wikipedia.org/wiki/Okapi_BM25

    BM25+ was developed to address one deficiency of the standard BM25 in which the component of term frequency normalization by document length is not properly lower-bounded; as a result of this deficiency, long documents which do match the query term can often be scored unfairly by BM25 as having a similar relevancy to shorter documents that do ...

  5. n-gram - Wikipedia

    en.wikipedia.org/wiki/N-gram

    Ngram Extractor: Gives weight of n-gram based on their frequency. Google's Google Books n-gram viewer and Web n-grams database (September 2006) STATOPERATOR N-grams Project Weighted n-gram viewer for every domain in Alexa Top 1M; 1,000,000 most frequent 2,3,4,5-grams from the 425 million word Corpus of Contemporary American English

  6. Bag-of-words model - Wikipedia

    en.wikipedia.org/wiki/Bag-of-words_model

    It disregards word order (and thus most of syntax or grammar) but captures multiplicity. The bag-of-words model is commonly used in methods of document classification where, for example, the (frequency of) occurrence of each word is used as a feature for training a classifier. [1] It has also been used for computer vision. [2]

  7. Word n-gram language model - Wikipedia

    en.wikipedia.org/wiki/Word_n-gram_language_model

    To prevent a zero probability being assigned to unseen words, each word's probability is slightly lower than its frequency count in a corpus. To calculate it, various methods were used, from simple "add-one" smoothing (assign a count of 1 to unseen n -grams, as an uninformative prior ) to more sophisticated models, such as Good–Turing ...

  8. Vector space model - Wikipedia

    en.wikipedia.org/wiki/Vector_space_model

    It contains incremental (memory-efficient) algorithms for term frequency-inverse document frequency, latent semantic indexing, random projections and latent Dirichlet allocation. Weka. Weka is a popular data mining package for Java including WordVectors and Bag Of Words models. Word2vec. Word2vec uses vector spaces for word embeddings.

  9. Document-term matrix - Wikipedia

    en.wikipedia.org/wiki/Document-term_matrix

    Certain function words such as and, the, at, a, etc., were placed in a "forbidden word list" table, and the frequency of these words was recorded in a separate listing... A special computer program, called the Descriptor Word Index Program, was written to provide this information and to prepare a document-term matrix in a form suitable for in ...