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| faq:howitworks [2009/04/06 09:50] – created xuesheng | faq:howitworks [2009/04/07 13:51] (current) – external edit 127.0.0.1 | ||
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| POPFile uses a technique called Naive Bayes to calculate the probability that the words in an email mean that that email falls into a specific bucket. | POPFile uses a technique called Naive Bayes to calculate the probability that the words in an email mean that that email falls into a specific bucket. | ||
| - | A bucket is represented by a collection of words and their frequency. The set of buckets is called the corpus and determines | + | A bucket is represented by a collection of words and their frequency. The set of buckets is called the corpus and determines |
| Suppose there are n buckets B1 to Bn and there are m words in total W1 to Wm. We want to know for a specific email E which bucket it is most likely to belong to. | Suppose there are n buckets B1 to Bn and there are m words in total W1 to Wm. We want to know for a specific email E which bucket it is most likely to belong to. | ||
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| We want to calculate the P(Bi|E) for each bucket Bi. That calculation can be performed using Bayes rule as follows | We want to calculate the P(Bi|E) for each bucket Bi. That calculation can be performed using Bayes rule as follows | ||
| - | P(E|Bi) x P(Bi) | + | P(E|Bi) x P(Bi) |
| P(Bi|E) = --------------- | P(Bi|E) = --------------- | ||
| - | | + | P(E) |
| Here P(Bi|E) is the probability that email E is in bucket Bi; that is the probability that given a set of words E they appear in bucket Bi. | Here P(Bi|E) is the probability that email E is in bucket Bi; that is the probability that given a set of words E they appear in bucket Bi. | ||
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