tf
Computes a score factor based on a term or phrase's frequency in a document. This value is multiplied by the .idf factor for each term in the query and these products are then summed to form the initial score for a document.
Terms and phrases repeated in a document indicate the topic of the document, so implementations of this method usually return larger values when freq is large, and smaller values when freq is small.
Return
a score factor based on a term's within-document frequency
Parameters
freq
the frequency of a term within a document