textproc/libtextcat 2.2 MidnightBSD

Libtextcat is a library with functions that implement the classification technique described in Cavnar & Trenkle, "N-Gram-Based Text Categorization" [1]. It was primarily developed for language guessing, a task on which it is known to perform with near-perfect accuracy.

The central idea of the Cavnar & Trenkle technique is to calculate a "fingerprint" of a document with an unknown category, and compare this with the fingerprints of a number of documents of which the categories are known. The categories of the closest matches are output as the classification. A fingerprint is a list of the most frequent n-grams occurring in a document, ordered by frequency. Fingerprints are compared with a simple out-of-place metric.

[1] The document that started it all: William B. Cavnar & John M. Trenkle (1994) N-Gram-Based Text Categorization, <http://citeseer.ist.psu.edu/68861.html>.