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

Classes in this File	Line Coverage	Branch Coverage	Complexity
FirstMoment	100%	100%	1.2;1.2

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
22		/**
23		* Computes the first moment (arithmetic mean). Uses the definitional formula:
24		* <p>
25		* mean = sum(x_i) / n
26		* <p>
27		* where <code>n</code> is the number of observations.
28		* <p>
29		* To limit numeric errors, the value of the statistic is computed using the
30		* following recursive updating algorithm:
31		* <p>
32		* <ol>
33		* <li>Initialize <code>m = </code> the first value</li>
34		* <li>For each additional value, update using <br>
35		* <code>m = m + (new value - m) / (number of observations)</code></li>
36		* </ol>
37		* <p>
38		* Returns <code>Double.NaN</code> if the dataset is empty.
39		* <p>
40		* <strong>Note that this implementation is not synchronized.</strong> If
41		* multiple threads access an instance of this class concurrently, and at least
42		* one of the threads invokes the <code>increment()</code> or
43		* <code>clear()</code> method, it must be synchronized externally.
44		*
45		* @version $Revision$ $Date: 2005-02-26 05:11:52 -0800 (Sat, 26 Feb 2005) $
46		*/
47		public class FirstMoment extends AbstractStorelessUnivariateStatistic
48		implements Serializable {
49
50		/** Serializable version identifier */
51		static final long serialVersionUID = -803343206421984070L;
52
53		/** Count of values that have been added */
54		protected long n;
55
56		/** First moment of values that have been added */
57		protected double m1;
58
59		/**
60		* Deviation of most recently added value from previous first moment.
61		* Retained to prevent repeated computation in higher order moments.
62		*/
63		protected double dev;
64
65		/**
66		* Deviation of most recently added value from previous first moment,
67		* normalized by previous sample size. Retained to prevent repeated
68		* computation in higher order moments
69		*/
70		protected double nDev;
71
72		/**
73		* Create a FirstMoment instance
74		*/
75	10784	public FirstMoment() {
76	10784	n = 0;
77	10784	m1 = Double.NaN;
78	10784	dev = Double.NaN;
79	10784	nDev = Double.NaN;
80	10784	}
81
82		/**
83		* @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#increment(double)
84		*/
85		public void increment(final double d) {
86	133804	if (n == 0) {
87	4710	m1 = 0.0;
88		}
89	133804	n++;
90	133804	double n0 = (double) n;
91	133804	dev = d - m1;
92	133804	nDev = dev / n0;
93	133804	m1 += nDev;
94	133804	}
95
96		/**
97		* @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#clear()
98		*/
99		public void clear() {
100	508	m1 = Double.NaN;
101	508	n = 0;
102	508	dev = Double.NaN;
103	508	nDev = Double.NaN;
104	508	}
105
106		/**
107		* @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getResult()
108		*/
109		public double getResult() {
110	100	return m1;
111		}
112
113		/**
114		* @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getN()
115		*/
116		public long getN() {
117	664	return n;
118		}
119		}