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From yo...@apache.org
Subject svn commit: r826529 - /lucene/solr/trunk/src/java/org/apache/solr/search/function/ReciprocalFloatFunction.java
Date Sun, 18 Oct 2009 21:35:36 GMT
Author: yonik
Date: Sun Oct 18 21:35:35 2009
New Revision: 826529

URL: http://svn.apache.org/viewvc?rev=826529&view=rev
Log:
javadoc - new ms() based example for date boosting

Modified:
    lucene/solr/trunk/src/java/org/apache/solr/search/function/ReciprocalFloatFunction.java

Modified: lucene/solr/trunk/src/java/org/apache/solr/search/function/ReciprocalFloatFunction.java
URL: http://svn.apache.org/viewvc/lucene/solr/trunk/src/java/org/apache/solr/search/function/ReciprocalFloatFunction.java?rev=826529&r1=826528&r2=826529&view=diff
==============================================================================
--- lucene/solr/trunk/src/java/org/apache/solr/search/function/ReciprocalFloatFunction.java
(original)
+++ lucene/solr/trunk/src/java/org/apache/solr/search/function/ReciprocalFloatFunction.java
Sun Oct 18 21:35:35 2009
@@ -25,17 +25,20 @@
 
 /**
  * <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 {



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