Java 计算（偏差
计算（经偏差校正的样本）方差。
实例源码：
源代码：
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//package com.nowjava;/*from n o w j a v a . c o m*/4
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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(variance(v));15
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}17
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/**20
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* Computes the (bias-corrected sample) variance.22
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*/24
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public static double variance(double[] v) {26
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if (v.length > 1) {28
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final double m = mean(v);//N o w J a v a . c o m 提 供30
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double ans = 0.0;32
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for (int i = 0; i < v.length; i++)34
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ans += (v[i] - m) * (v[i] - m);36
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return ans / (v.length - 1);38
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} else40
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throw new IllegalArgumentException(42
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"Array length must be of 2 or greater.");44
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}46
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/**49
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* Computes the (bias-corrected sample) variance.51
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*/53
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public static double variance(int[] v) {55
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if (v.length > 1) {57
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final double m = mean(v);59
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double ans = 0.0;61
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for (int i = 0; i < v.length; i++)63
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ans += (v[i] - m) * (v[i] - m);65
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return ans / (v.length - 1);67
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} else69
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throw new IllegalArgumentException(71
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"Array length must be of 2 or greater.");73
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}75
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/**78
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* Computes the mean.80
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*/82
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public static double mean(double[] v) {84
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if (v.length == 0)86
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throw new IllegalArgumentException(88
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"Nothing to compute! The array must have at least one element.");90
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return (mass(v) / (double) v.length);92
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}94
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/**97
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* Computes the mean.99
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*/101
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public static double mean(int[] v) {103
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if (v.length == 0)105
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throw new IllegalArgumentException(107
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"Nothing to compute! The array must have at least one element.");109
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return (mass(v) / (double) v.length);111
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}113
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/**116
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* Returns the sum of the elements of the array.118
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*/120
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public static double mass(double[] v) {122
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double somme = 0.0;124
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