The formula hasn't changed (but the first printing of the book had a portion of it missing, check javadoc for (Default?)Similarity for the real and current formula).
Here is a simple IDF example, or at least how I "visualize" IDF. You have an index with a bunch of documents and terms in it. A term T can appear some number of times in this index, say N times. You can think of the IDF of the term T is "1/N" (not really 1/N, but.... log(numDocs/(docFreq+1)) + 1). The more frequent the term in the index, the smaller its weight (the less important it is during scoring). Otis ----- Original Message ---- From: Rajiv Roopan <[EMAIL PROTECTED]> To: java-user@lucene.apache.org Sent: Thursday, July 6, 2006 10:46:52 PM Subject: Lucene search formula Hello, I was recently looking thru the lucene in action book and came across the scoring formula. I was wondering if the formula has changed since the book was written? Also was wondering if someone can breifly explain what the IDF(t) term in the formula means? In the book it says that it's the inverse document frequency of the term but doesn't explain beyond that? thanks, rajiv --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
