Differences
This shows you the differences between two versions of the page.
| Next revision | Previous revision | ||
| faq:bayesandlogs [2009/04/06 09:52] – created xuesheng | faq:bayesandlogs [2009/04/07 13:54] (current) – external edit 127.0.0.1 | ||
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| POPFile makes use of Bayes Theorem in the form: | POPFile makes use of Bayes Theorem in the form: | ||
| - | | + | P(E|Bi) x P(Bi) |
| P(Bi|E) = --------------- | P(Bi|E) = --------------- | ||
| P(E) | P(E) | ||
| Line 27: | Line 27: | ||
| POPFile ignores the term P(E) since it is the same for each calculation and calculates: | POPFile ignores the term P(E) since it is the same for each calculation and calculates: | ||
| - | (1) P(Bi|E) = P(E1|Bi) x P(E2|Bi) x ... x P(Eo|Bi) x P(Bi) | + | |
| And picks the largest to determine which bucket the email belongs in. But equation (1) works well in theory and badly in practice. | And picks the largest to determine which bucket the email belongs in. But equation (1) works well in theory and badly in practice. | ||
| Line 37: | Line 37: | ||
| POPFile calculates the following: | POPFile calculates the following: | ||
| - | (2) log P(Bi|E) = log P(E1|Bi) + log P(E2|Bi) + ... + P(Eo|Bi) + log P(Bi) | + | |
| and then chooses the largest value of log P(Bi|E) in determining the bucket. | and then chooses the largest value of log P(Bi|E) in determining the bucket. | ||
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