[Python-Dev] Re: [Python-checkins]
Tue, 20 Aug 2002 19:44:52 -0400
> Some perhaps relevant links (with no off-topic discusssion):
> * http://www.tuxedo.org/~esr/bogofilter/
Damn -- wish I'd read that before. Among other things, Eric found a good
use for Judy arrays <wink>.
> * http://www.ai.mit.edu/~jrennie/ifile/
Knew about that. Good stuff.
Seems confused, assuming Graham's approach is a minor variant of ifile's.
But Graham's computation is to classic Bayesian classifiers (like ifile) as
Python's lambda is to Lisp's <0.7 wink>. Heart of the confusion:
Integrating the whole set of statistics together requires adding up
statistics for _all_ the words found in a message, not just the
words "sex" and "sexy."
The rub is that Graham doesn't try to add up the statistics for all the
words found in a msg. To the contrary, it ends up ignoring almost all of
the words. In particular, if the database indicates that "sex" and "sexy"
aren't good spam-vs-non-spam discriminators, Graham's approach ignores them
completely (their presence or absence doesn't affect the final outcome at
all -- it's like the words don't exist; this isn't what ifile does, and
ifile probably couldn't get away with this because it's trying to do N-way
classification instead of strictly 2-way -- someone who understands the math
and reads Graham's article carefully will likely have a hard time figuring
out what Bayes has to do with it at all! I sure did.).
> """My finding is that it is _nowhere_ near sufficient to have two
> populations, "spam" versus "not spam."
In ifile I believe that. But the data will speak for itself soon enough, so
I'm not going to argue about this.