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javadoc - new ms() based example for date boosting

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git-svn-id: https://svn.apache.org/repos/asf/lucene/solr/trunk@826529 13f79535-47bb-0310-9956-ffa450edef68
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Yonik Seeley 2009-10-18 21:35:35 +00:00
parent a659c981e9
commit de1f9c752a
1 changed files with 7 additions and 4 deletions
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src/java/org/apache/solr/search/function/ReciprocalFloatFunction.java
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@ -25,17 +25,20 @@ import java.util.Map;
/**
* <code>ReciprocalFloatFunction</code> implements a reciprocal function f(x) = a/(mx+b), based on
* the float value of a field as exported by {@link org.apache.solr.search.function.ValueSource}.
* the float value of a field or function as exported by {@link org.apache.solr.search.function.ValueSource}.
* <br>
*
* When a and b are equal, and x>=0, this function has a maximum value of 1 that drops as x increases.
* Increasing the value of a and b together results in a movement of the entire function to a flatter part of the curve.
* <br>These properties make this an idea function for boosting more recent documents.
* <br>Example:<code>ReciprocalFloatFunction(new ReverseOrdFieldSource("my_date"),1,1000,1000)</code>
* <p>These properties make this an idea function for boosting more recent documents.
* <p>Example:<code> recip(ms(NOW,mydatefield),3.16e-11,1,1)</code>
* <p>A multiplier of 3.16e-11 changes the units from milliseconds to years (since there are about 3.16e10 milliseconds
* per year). Thus, a very recent date will yield a value close to 1/(0+1) or 1,
* a date a year in the past will get a multiplier of about 1/(1+1) or 1/2,
* and date two years old will yield 1/(2+1) or 1/3.
*
* @see FunctionQuery
*
*
* @version $Id$
*/
public class ReciprocalFloatFunction extends ValueSource {