# Different Weights to Lucene fields with Okapi Similarity

Based on this link http://www2002.org/CDROM/refereed/643/node6.html , I'm calculating Okapi similarity between the query document and another document as below using Lucene:

I have indexed the documents using 3 fields. I want to give higher weight to field 2 and field 3. I can't use Lucene's boost function since i'm using a my own similarity function. Can anyone suggest me a method how to give different weights to fields using this Okapi Similarity function?

This is Okapi Similarity Schema that I have used

sim(query, doc) = sum(t in terms(query), freq(t, query) * w(t, doc))


where (from the second link, slightly modified as I think the formula in the link is incorrect)

w(t, doc) = idf(t) * (k+1)*freq(t, doc) / (k*(1-b + b*ls(doc)) + freq(t, doc))
ls(doc) = len(doc)/avgdoclen


and idf(t) is idf(t) = log (totalNumIndexedDocs - docFreq + 0.5)/(docFreq + 0.5), freq(t, doc) is the frequency of term t in document doc.

Choosing b=0.25 and k = 1.2 , get

w(t, doc) = idf(t) * 2.2*freq(t, doc) / (1.2*(0.25+0.75*ls(doc)) + freq(t, doc))


(I posted the same question in Stackoverflow http://stackoverflow.com/questions/11098597/different-weights-to-lucene-fields-with-okapi-similarity did't get an answer. So I thought to post here, hope my question is not irrelevant for this forum)

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 I have noticed your question has not received much attention. Have you tried posting your question in a forum specific to Lucene users? – Paul♦ Jul 16 '12 at 21:28 @Paul, yes I have posted this on java-user@lucene.apache.org mailing list too, but no one gave any response. Do you know somewhere else that I can post this, that may get attention? – Kasun Jul 17 '12 at 3:12