Java 计算（偏差
计算数组的（偏差校正后的样本）标准偏差。
实例源码：
源代码：
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//package com.nowjava;4
/** 来 自 n o w j a v a . c o m - 时 代 Java**/5
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public class Main {7
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public static void main(String[] argv) throws Exception {9
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double[] v = new double[] { 34.45, 35.45, 36.67, 37.78, 37.0000,11
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37.1234, 67.2344, 68.34534, 69.87700 };13
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System.out.println(standardDeviation(v));15
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}17
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/**20
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* Computes the (bias-corrected sample) standard deviation of an array.22
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*/24
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public static double standardDeviation(double[] v) {26
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return (Math.sqrt(variance(v)));28
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}30
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/**33
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* Returns the (bias-corrected sample) standard deviation of an array.35
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*/37
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public static double standardDeviation(int[] v) {39
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return (Math.sqrt(variance(v)));41
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}//from 时 代 J a v a - nowjava.com43
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/**46
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* Computes the (bias-corrected sample) variance.48
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*/50
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public static double variance(double[] v) {52
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if (v.length > 1) {54
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final double m = mean(v);56
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double ans = 0.0;58
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for (int i = 0; i < v.length; i++)60
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ans += (v[i] - m) * (v[i] - m);62
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return ans / (v.length - 1);64
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} else66
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throw new IllegalArgumentException(68
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"Array length must be of 2 or greater.");70
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}72
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/**75
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* Computes the (bias-corrected sample) variance.77
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*/79
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public static double variance(int[] v) {81
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if (v.length > 1) {83
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final double m = mean(v);85
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double ans = 0.0;87
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for (int i = 0; i < v.length; i++)89
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ans += (v[i] - m) * (v[i] - m);91
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return ans / (v.length - 1);93
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} else95
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throw new IllegalArgumentException(97
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"Array length must be of 2 or greater.");99
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}101
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/**104
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* Computes the mean.106
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*/108
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public static double mean(double[] v) {110
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if (v.length == 0)112
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throw new IllegalArgumentException(114
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"Nothing to compute! The array must have at least one element.");116
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return (mass(v) / (double) v.length);118
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}120
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/**123
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* Computes the mean.125
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*/127
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public static double mean(int[] v) {129
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if (v.length == 0)131
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throw new IllegalArgumentException(133
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"Nothing to compute! The array must have at least one element.");135
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return (mass(v) / (double) v.length);137
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}139
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/**142
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* Returns the sum of the elements of the array.144
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*/146
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