Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||||||
SumOfSquares |
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| 1.5;1.5 |
1 | /* |
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2 | * Copyright 2003-2004 The Apache Software Foundation. |
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3 | * |
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4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
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5 | * you may not use this file except in compliance with the License. |
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6 | * You may obtain a copy of the License at |
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7 | * |
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8 | * http://www.apache.org/licenses/LICENSE-2.0 |
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9 | * |
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10 | * Unless required by applicable law or agreed to in writing, software |
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11 | * distributed under the License is distributed on an "AS IS" BASIS, |
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12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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13 | * See the License for the specific language governing permissions and |
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14 | * limitations under the License. |
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15 | */ |
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16 | package org.apache.commons.math.stat.descriptive.summary; |
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17 | ||
18 | import java.io.Serializable; |
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19 | ||
20 | import org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic; |
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21 | ||
22 | /** |
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23 | * Returns the sum of the squares of the available values. |
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24 | * <p> |
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25 | * If there are no values in the dataset, or any of the values are |
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26 | * <code>NaN</code>, then <code>NaN</code> is returned. |
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27 | * <p> |
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28 | * <strong>Note that this implementation is not synchronized.</strong> If |
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29 | * multiple threads access an instance of this class concurrently, and at least |
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30 | * one of the threads invokes the <code>increment()</code> or |
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31 | * <code>clear()</code> method, it must be synchronized externally. |
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32 | * |
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33 | * @version $Revision$ $Date: 2005-02-26 05:11:52 -0800 (Sat, 26 Feb 2005) $ |
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34 | */ |
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35 | public class SumOfSquares extends AbstractStorelessUnivariateStatistic implements Serializable { |
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36 | ||
37 | /** Serializable version identifier */ |
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38 | static final long serialVersionUID = 1460986908574398008L; |
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39 | ||
40 | /** */ |
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41 | private long n; |
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42 | ||
43 | /** |
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44 | * The currently running sumSq |
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45 | */ |
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46 | private double value; |
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47 | ||
48 | /** |
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49 | * Create a SumOfSquares instance |
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50 | */ |
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51 | 10206 | public SumOfSquares() { |
52 | 10206 | n = 0; |
53 | 10206 | value = Double.NaN; |
54 | 10206 | } |
55 | ||
56 | /** |
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57 | * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#increment(double) |
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58 | */ |
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59 | public void increment(final double d) { |
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60 | 131576 | if (n == 0) { |
61 | 4472 | value = d * d; |
62 | } else { |
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63 | 127104 | value += d * d; |
64 | } |
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65 | 131576 | n++; |
66 | 131576 | } |
67 | ||
68 | /** |
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69 | * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getResult() |
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70 | */ |
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71 | public double getResult() { |
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72 | 560 | return value; |
73 | } |
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74 | ||
75 | /** |
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76 | * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getN() |
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77 | */ |
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78 | public long getN() { |
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79 | 58 | return n; |
80 | } |
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81 | ||
82 | /** |
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83 | * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#clear() |
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84 | */ |
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85 | public void clear() { |
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86 | 38 | value = Double.NaN; |
87 | 38 | n = 0; |
88 | 38 | } |
89 | ||
90 | /** |
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91 | * Returns the sum of the squares of the entries in the specified portion of |
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92 | * the input array, or <code>Double.NaN</code> if the designated subarray |
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93 | * is empty. |
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94 | * <p> |
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95 | * Throws <code>IllegalArgumentException</code> if the array is null. |
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96 | * |
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97 | * @param values the input array |
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98 | * @param begin index of the first array element to include |
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99 | * @param length the number of elements to include |
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100 | * @return the sum of the squares of the values or Double.NaN if length = 0 |
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101 | * @throws IllegalArgumentException if the array is null or the array index |
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102 | * parameters are not valid |
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103 | */ |
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104 | public double evaluate(final double[] values,final int begin, final int length) { |
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105 | 42 | double sumSq = Double.NaN; |
106 | 42 | if (test(values, begin, length)) { |
107 | 34 | sumSq = 0.0; |
108 | 214 | for (int i = begin; i < begin + length; i++) { |
109 | 180 | sumSq += values[i] * values[i]; |
110 | } |
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111 | } |
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112 | 40 | return sumSq; |
113 | } |
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114 | ||
115 | } |