Inverse document-frequency scaling matrix
This function creates an inverse-document-frequency (IDF)
scaling matrix from a document-term matrix. The IDF is defined as follows:
idf = log(# documents in the corpus) / (# documents where the term
appears + 1)
get_idf(dtm, log_scale = log, smooth_idf = TRUE)
- a document-term matrix of class
functionto use in calculating the IDF matrix. Usually log is used, but it might be worth trying log2.
logicalsmooth IDF weights by adding one to document frequencies, as if an extra document was seen containing every term in the collection exactly once. This prevents division by zero.
ddiMatrixIDF scaling diagonal sparse matrix.
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