Coverage Report - org.apache.commons.math.stat.descriptive.moment.GeometricMean

Classes in this File Line Coverage Branch Coverage Complexity
GeometricMean
100% 
100% 
1.333

 1  
 /*
 2  
  * Copyright 2003-2004 The Apache Software Foundation.
 3  
  *
 4  
  * Licensed under the Apache License, Version 2.0 (the "License");
 5  
  * you may not use this file except in compliance with the License.
 6  
  * You may obtain a copy of the License at
 7  
  *
 8  
  *      http://www.apache.org/licenses/LICENSE-2.0
 9  
  *
 10  
  * Unless required by applicable law or agreed to in writing, software
 11  
  * distributed under the License is distributed on an "AS IS" BASIS,
 12  
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 13  
  * See the License for the specific language governing permissions and
 14  
  * limitations under the License.
 15  
  */
 16  
 package org.apache.commons.math.stat.descriptive.moment;
 17  
 
 18  
 import org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic;
 19  
 import org.apache.commons.math.stat.descriptive.summary.SumOfLogs;
 20  
 
 21  
 /**
 22  
  * Returns the <a href="http://www.xycoon.com/geometric_mean.htm">
 23  
  * geometric mean </a> of the available values.
 24  
  * <p>
 25  
  * Uses a {@link SumOfLogs} instance to compute sum of logs and returns
 26  
  * <code> exp( 1/n  (sum of logs) ).</code>  Therefore,
 27  
  * <ul>
 28  
  * <li>If any of values are < 0, the result is <code>NaN.</code></li>
 29  
  * <li>If all values are non-negative and less than 
 30  
  * <code>Double.POSITIVE_INFINITY</code>,  but at least one value is 0, the 
 31  
  * result is <code>0.</code></li>
 32  
  * <li>If both <code>Double.POSITIVE_INFINITY</code> and 
 33  
  * <code>Double.NEGATIVE_INFINITY</code> are among the values, the result is
 34  
  * <code>NaN.</code></li>
 35  
  * </ul>
 36  
  * <p>
 37  
  * <strong>Note that this implementation is not synchronized.</strong> If 
 38  
  * multiple threads access an instance of this class concurrently, and at least
 39  
  * one of the threads invokes the <code>increment()</code> or 
 40  
  * <code>clear()</code> method, it must be synchronized externally.
 41  
  * 
 42  
  *
 43  
  * @version $Revision$ $Date: 2005-02-26 05:11:52 -0800 (Sat, 26 Feb 2005) $
 44  
  */
 45  
 public class GeometricMean extends AbstractStorelessUnivariateStatistic {
 46  
 
 47  
     /** Serializable version identifier */
 48  
     static final long serialVersionUID = -8178734905303459453L;  
 49  
     
 50  
     /** Wrapped SumOfLogs instance */
 51  
     private SumOfLogs sumOfLogs;
 52  
 
 53  
     /**
 54  
      * Create a GeometricMean instance
 55  
      */
 56  10210
     public GeometricMean() {
 57  10210
         sumOfLogs = new SumOfLogs();
 58  10210
     }
 59  
     
 60  
     /**
 61  
      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#increment(double)
 62  
      */
 63  
     public void increment(final double d) {
 64  131576
         sumOfLogs.increment(d);
 65  131576
     }
 66  
 
 67  
     /**
 68  
      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getResult()
 69  
      */
 70  
     public double getResult() {
 71  606
         if (sumOfLogs.getN() > 0) {
 72  430
             return Math.exp(sumOfLogs.getResult() / (double) sumOfLogs.getN());
 73  
         } else {
 74  176
             return Double.NaN;
 75  
         }
 76  
     }
 77  
 
 78  
     /**
 79  
      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#clear()
 80  
      */
 81  
     public void clear() {
 82  40
         sumOfLogs.clear();
 83  40
     }
 84  
 
 85  
     /**
 86  
      * Returns the geometric mean of the entries in the specified portion
 87  
      * of the input array.
 88  
      * <p>
 89  
      * See {@link GeometricMean} for details on the computing algorithm.
 90  
      * <p>
 91  
      * Throws <code>IllegalArgumentException</code> if the array is null.
 92  
      * 
 93  
      * @param values input array containing the values
 94  
      * @param begin first array element to include
 95  
      * @param length the number of elements to include
 96  
      * @return the geometric mean or Double.NaN if length = 0 or
 97  
      * any of the values are &lt;= 0.
 98  
      * @throws IllegalArgumentException if the input array is null or the array
 99  
      * index parameters are not valid
 100  
      */
 101  
     public double evaluate(
 102  
         final double[] values, final int begin, final int length) {
 103  34
         return Math.exp(
 104  
             sumOfLogs.evaluate(values, begin, length) / (double) length);
 105  
     }
 106  
     
 107  
     /**
 108  
      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getN()
 109  
      */
 110  
     public long getN() {
 111  58
         return sumOfLogs.getN();
 112  
     }
 113  
 
 114  
 }