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Date: Fri, 3 Mar 2006 10:36:08 +0800
From: "Eugene Ezekiel" <echothis@gmail.com>
To: java-user@lucene.apache.org
Subject: Re: Help interpreting explanation
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Thanks Yonik for the reply. I got just a couple more questions,

1) Why does the explanantion print so  many times?

2) Since my query is made up of multiple terms how do I know what term "x"
is referring to?


On 3/3/06, Yonik Seeley <yseeley@gmail.com> wrote:
>
> I think Lucene in Action does a good job of it.
> There is also a formula given in the javadoc for DefaultSimilarity
>
> http://lucene.apache.org/java/docs/api/org/apache/lucene/search/Similarit=
y.html
>
> See my comments below (inline)
>
> On 3/2/06, Eugene <echothis@gmail.com> wrote:
> > Hi All,
> >
> > I'm not sure how to interpret the result of the toString method of
> > Explanation.  I'm trying to see the values of each component of the
> > Default Similarity formula for a particular query and a doc.  Given
> > below is a sample of my Explanation output. Many thanks if anyone could
> > help explain some of the values or direct me to a place that does so.
> >
> > Explanation =3D 0.683103 =3D product of:
> >    1.7077575 =3D sum of:
> >      0.184242 =3D weight(Contents:x in 78), product of:
> >        0.13565542 =3D queryWeight(Contents:x), product of:
> the queryWeight is query-specific... it will have the same value
> for all documents matching the query.
> >          2.509232 =3D idf(docFreq=3D85)
> inverse document frequency... term "x" appears in 85 documents.
> >          0.054062527 =3D queryNorm
> queryNorm is a normalization factor... 1/sqrt(sum of all query weights
> squared)
>
> If you had a boost, it would also be multiplied into the queryWeight
> at this point.
> >        1.3581617 =3D fieldWeight(Contents:x in 78), product of:
> fieldWeight components are document specific.
> >          1.7320508 =3D tf(termFreq(Contents:x)=3D3)
> "x" appears 3 times in the field for this document
> >          2.509232 =3D idf(docFreq=3D85)
> same as the previous idf factor - 85 documents contain "x"
> >          0.3125 =3D fieldNorm(field=3DContents, doc=3D78)
> the norm is calculated at index time... it's the length normalization
> factor (1/sqrt(num tokens in this field)) multipled by any on the
> field or document.
>
> >      0.184242 =3D weight(Contents:x in 78), product of:
> >        0.13565542 =3D queryWeight(Contents:x), product of:
> >          2.509232 =3D idf(docFreq=3D85)
> >          0.054062527 =3D queryNorm
> >        1.3581617 =3D fieldWeight(Contents:x in 78), product of:
> >          1.7320508 =3D tf(termFreq(Contents:x)=3D3)
> >          2.509232 =3D idf(docFreq=3D85)
> >          0.3125 =3D fieldNorm(field=3DContents, doc=3D78)
> >      0.26218253 =3D weight(Contents:y in 78), product of:
> >        0.16182467 =3D queryWeight(Contents:y), product of:
> >          2.9932873 =3D idf(docFreq=3D52)
> >          0.054062527 =3D queryNorm
> >        1.6201642 =3D fieldWeight(Contents:y in 78), product of:
> >          1.7320508 =3D tf(termFreq(Contents:y)=3D3)
> >          2.9932873 =3D idf(docFreq=3D52)
> >          0.3125 =3D fieldNorm(field=3DContents, doc=3D78)
>
>
> -Yonik
>
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>


--
Regards,
Eugene

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