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From pste...@apache.org
Subject cvs commit: jakarta-commons/math/src/java/org/apache/commons/math/stat/univariate/moment GeometricMean.java
Date Fri, 18 Jun 2004 07:03:40 GMT
psteitz     2004/06/18 00:03:40

  Modified:    math/src/java/org/apache/commons/math/stat/univariate/moment
                        GeometricMean.java
  Log:
  Improved javadoc, implementation.
  
  Revision  Changes    Path
  1.19      +20 -15    jakarta-commons/math/src/java/org/apache/commons/math/stat/univariate/moment/GeometricMean.java
  
  Index: GeometricMean.java
  ===================================================================
  RCS file: /home/cvs/jakarta-commons/math/src/java/org/apache/commons/math/stat/univariate/moment/GeometricMean.java,v
  retrieving revision 1.18
  retrieving revision 1.19
  diff -u -r1.18 -r1.19
  --- GeometricMean.java	27 Apr 2004 16:42:30 -0000	1.18
  +++ GeometricMean.java	18 Jun 2004 07:03:40 -0000	1.19
  @@ -21,7 +21,20 @@
   
   /**
    * Returns the <a href="http://www.xycoon.com/geometric_mean.htm">
  - * geometric mean </a> of the available values
  + * geometric mean </a> of the available values.
  + * <p>
  + * Uses {@link SumOfLogs} superclass to compute sum of logs and returns
  + * <code> exp( 1/n  (sum of logs) ).</code>  Therefore,
  + * <ul>
  + * <li>If any of values are < 0, the result is <code>NaN.</code></li>
  + * <li>If all values are non-negative and less than <code>Double.POSITIVE_INFINITY</code>,

  + * but at least one value is 0, the result is <code>0.</code></li>
  + * <li>If both <code>Double.POSITIVE_INFINITY</code> and 
  + * <code>Double.NEGATIVE_INFINITY</code> are among the values, the result is
  + * <code>NaN.</code></li>
  + * </ul>
  + * 
  + * 
    * @version $Revision$ $Date$
    */
   public class GeometricMean extends SumOfLogs implements Serializable{
  @@ -29,15 +42,9 @@
       /** Serializable version identifier */
       static final long serialVersionUID = -8178734905303459453L;  
         
  -    /** */
  +    /**Number of values that have been added */
       protected long n = 0;
   
  -    /** */
  -    private double geoMean = Double.NaN;
  -
  -    /** */
  -    private double lastSum = 0.0;
  -
       /**
        * @see org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic#increment(double)
        */
  @@ -50,11 +57,11 @@
        * @see org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic#getResult()
        */
       public double getResult() {
  -        if (lastSum != super.getResult() || n == 1) {
  -            lastSum = super.getResult();
  -            geoMean = Math.exp(lastSum / (double) n);
  +        if (n > 0) {
  +            return Math.exp(super.getResult() / (double) n);
  +        } else {
  +            return Double.NaN;
           }
  -        return geoMean;
       }
   
       /**
  @@ -62,8 +69,6 @@
        */
       public void clear() {
           super.clear();
  -        lastSum = 0.0;
  -        geoMean = Double.NaN;
           n = 0;
       }
   
  
  
  

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