RcmdrPlugin.temis (version 0.6.1)

termFrequencies: Frequency of chosen terms in the corpus

Description

List terms with the highest number of occurrences in the document-term matrix of a corpus, possibly grouped by the levels of a variable.

Usage

termFrequencies(dtm, terms, variable = NULL, n = 25, by.term = FALSE)

Arguments

dtm

a document-term matrix.

terms

one or more terms, i.e. column names of dtm.

variable

a vector whose length is the number of rows of dtm, or NULL to report most frequent terms by document; use NA to report most frequent terms in the whole corpus.

n

the number of terms to report for each level.

by.term

whether the third dimension of the array should be terms instead of levels.

Value

• If variable = NA, one matrix with columns Global and Global % (see below). Else, an array with seven columns:
• % Term/Level
  the percent of the term's occurrences in all terms occurrences in the level.
• % Level/Term
  the percent of the term's occurrences that appear in the level (rather than in other levels).
• Global %
  the percent of the term's occurrences in all terms occurrences in the corpus.
• Global
  the number of occurrences of the term in the corpus.
• Level
  the number of occurrences of the term (internal).
• t value
  the quantile of a normal distribution corresponding the probability Prob..
• Prob.
  the probability of observing such an extreme (high or low) number of occurrences of the term in the level, under an hypergeometric distribution.

Details

The probability is that of observing such extreme frequencies of the considered term in the level, under an hypergeometric distribution based on its global frequency in the corpus and on the number of occurrences of all terms in the document or variable level considered. The positive or negative character of the association is visible from the sign of the t value, or by comparing the value of the % Term/Level column with that of the Global % column.

See Also

specificTerms, DocumentTermMatrix