Authorship Attribution Using the Chaos Game Representation
Table 1: The equivalence classes and their corresponding base 4 representation.
['Class {b, d}', 'Base 4 00', 'Class {p}', 'Base 4 20']
The most successful representation among the ones tried is obtained by encoding each distinct character as a pair of numbers in base 4. There are only 16 different pairs of numbers in base 4, so some characters are replaced by others in the initial text in order to reach only 16 equivalence classes. The classes of characters are chosen and ordered so that several criteria are met: The letters that are very common are left alone in order to reach a rough balance with respect to the occurrence of each equivalence class of characters. The letters that are less common are grouped in the same equivalence class if they have similar sounds or similar phonetic usage. White space (tabs, spaces, and line breaks) are grouped into one equivalence class. The punctuation and the digits are gathered in the same class. Other characters (that do not belong to the Latin alphabet) are omitted. Beside the grouping of the characters, special attention is paid to the choice of the base 4 representation for each equivalence class. It is intended to have a good balance in the spread of characters that are encoded in base 4 and start, and end respectively, with a certain digit.