( For details and an explanation, check Jed Hartman's Blog here )
Playing with this, I discovered something interesting: the algorithm identified both a chunk of Edward II (A Gaveston speech) and a chunk of Kit's POV from The Stratford Man as female, and a chunk of Othello (Iago and Roderigo) and a chunk of Will's POV from SM as male.
Heh. Well, at least that tells me I've managed to give them somewhat different voices, I guess.
A sonnet, however, was identified as female.