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

Classes in this File	Line Coverage	Branch Coverage	Complexity
Mean	100%	100%	1.5714285714285714;1.571

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 java.io.Serializable;
19
20		import org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic;
21		import org.apache.commons.math.stat.descriptive.summary.Sum;
22
23		/**
24		* Returns the arithmetic mean of the available values. Uses the definitional
25		* formula:
26		* <p>
27		* mean = sum(x_i) / n
28		* <p>
29		* where <code>n</code> is the number of observations.
30		* <p>
31		* The value of the statistic is computed using the following recursive
32		* updating algorithm:
33		* <p>
34		* <ol>
35		* <li>Initialize <code>m = </code> the first value</li>
36		* <li>For each additional value, update using <br>
37		* <code>m = m + (new value - m) / (number of observations)</code></li>
38		* </ol>
39		* <p>
40		* Returns <code>Double.NaN</code> if the dataset is empty.
41		* <p>
42		* <strong>Note that this implementation is not synchronized.</strong> If
43		* multiple threads access an instance of this class concurrently, and at least
44		* one of the threads invokes the <code>increment()</code> or
45		* <code>clear()</code> method, it must be synchronized externally.
46		*
47		* @version $Revision$ $Date: 2005-02-26 05:11:52 -0800 (Sat, 26 Feb 2005) $
48		*/
49		public class Mean extends AbstractStorelessUnivariateStatistic
50		implements Serializable {
51
52		/** Serializable version identifier */
53		static final long serialVersionUID = -1296043746617791564L;
54
55		/** First moment on which this statistic is based. */
56		protected FirstMoment moment;
57
58		/**
59		* Determines whether or not this statistic can be incremented or cleared.
60		* <p>
61		* Statistics based on (constructed from) external moments cannot
62		* be incremented or cleared.
63		*/
64		protected boolean incMoment;
65
66		/** Constructs a Mean. */
67	352	public Mean() {
68	352	incMoment = true;
69	352	moment = new FirstMoment();
70	352	}
71
72		/**
73		* Constructs a Mean with an External Moment.
74		*
75		* @param m1 the moment
76		*/
77	16614	public Mean(final FirstMoment m1) {
78	16614	this.moment = m1;
79	16614	incMoment = false;
80	16614	}
81
82		/**
83		* @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#increment(double)
84		*/
85		public void increment(final double d) {
86	162	if (incMoment) {
87	162	moment.increment(d);
88		}
89	162	}
90
91		/**
92		* @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#clear()
93		*/
94		public void clear() {
95	22	if (incMoment) {
96	22	moment.clear();
97		}
98	22	}
99
100		/**
101		* @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getResult()
102		*/
103		public double getResult() {
104	16704	return moment.m1;
105		}
106
107		/**
108		* @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getN()
109		*/
110		public long getN() {
111	58	return moment.getN();
112		}
113
114		/**
115		* Returns the arithmetic mean of the entries in the specified portion of
116		* the input array, or <code>Double.NaN</code> if the designated subarray
117		* is empty.
118		* <p>
119		* Throws <code>IllegalArgumentException</code> if the array is null.
120		* <p>
121		* See {@link Mean} for details on the computing algorithm.
122		*
123		* @param values the input array
124		* @param begin index of the first array element to include
125		* @param length the number of elements to include
126		* @return the mean of the values or Double.NaN if length = 0
127		* @throws IllegalArgumentException if the array is null or the array index
128		* parameters are not valid
129		*/
130		public double evaluate(final double[] values,final int begin, final int length) {
131	496	if (test(values, begin, length)) {
132	476	Sum sum = new Sum();
133	476	return sum.evaluate(values, begin, length) / ((double) length);
134		}
135	18	return Double.NaN;
136		}
137		}