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Java 重新规范化数组，使其L2范数为1（直至计算错误）。
重新规范化数组，使其L2范数为1（直至计算错误）。
实例源码：
源代码：
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//package com.nowjava;4
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/*6
来 自*7
NowJava.com8
*/9
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public class Main {11
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public static void main(String[] argv) throws Exception {13
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double[] v = new double[] { 34.45, 35.45, 36.67, 37.78, 37.0000,15
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37.1234, 67.2344, 68.34534, 69.87700 };17
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System.out.println(java.util.Arrays.toString(normalize(v)));19
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}21
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/**24
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* Renormalizes the array so that its L2 norm is 126
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* (up to computational errors).28
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*/30
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public static double[] normalize(double[] v) {32
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return (scalarMultiply(1.0 / norm(v), v));34
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}36
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/**39
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* Returns a comma delimited string representing the value of the array.41
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*/43
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public static String toString(double[] array) {45
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StringBuffer buf = new StringBuffer(array.length);48
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int i;50
/*51
来 自*52
N o w J a v a . c o m - 时 代 Java53
*/54
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for (i = 0; i < array.length - 1; i++) {56
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buf.append(array[i]);58
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buf.append(',');60
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}62
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buf.append(array[i]);64
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return buf.toString();66
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}68
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/**71
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* Returns a comma delimited string representing the value of the array.73
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*/75
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public static String toString(double[][] array) {77
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StringBuffer buf = new StringBuffer();79
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for (int k = 0; k < array.length; k++) {81
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buf.append(toString(array[k]));83
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buf.append(System.getProperty("line.separator"));85
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}87
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return buf.toString();89
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}91
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/**94
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* Returns a comma delimited string representing the value of the array.96
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*/98
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public static String toString(int[] array) {100
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StringBuffer buf = new StringBuffer(array.length);102
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int i;104
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for (i = 0; i < array.length - 1; i++) {106
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buf.append(array[i]);108
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buf.append(',');110
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}112
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buf.append(array[i]);114
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return buf.toString();116
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}118
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/**121
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* Returns a comma delimited string representing the value of the array.123
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*/125
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public static String toString(int[][] array) {127
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StringBuffer buf = new StringBuffer();129
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for (int k = 0; k < array.length; k++) {131
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buf.append(toString(array[k]));133
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buf.append(System.getProperty("line.separator"));135
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}137
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return buf.toString();139
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}141
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/**144
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* Multiplies every component of an array by a scalar.146
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*/148
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public static double[] scalarMultiply(double a, double[] v) {150
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double[] ans = new double[v.length];152
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for (int k = 0; k < v.length; k++) {154
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ans[k] = a * v[k];156
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}158
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return (ans);160
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}162
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/**165
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* Multiplies every component of an array by a scalar.167
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*/169
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public static double[] scalarMultiply(double a, int[] v) {171
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double[] ans = new double[v.length];173
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for (int k = 0; k < v.length; k++) {175
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ans[k] = v[k] * a;177
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}179
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return (ans);181
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}183
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/**186
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* Computes the L2 norm of an array (Euclidean norm or "length").188
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*/190
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public static double norm(double[] data) {192
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return (Math.sqrt(sumSquares(data)));194
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}196
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/**199
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* Computes the L2 norm of an array (Euclidean norm or "length").201
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*/203
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public static double norm(int[] data) {205
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return (Math.sqrt(sumSquares(data)));207
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}209
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/**212
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* Sums the squares of all components;214
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* also called the energy of the array.216
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*/218
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public static double sumSquares(double[] data) {220
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double ans = 0.0;222
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for (int k = 0; k < data.length; k++) {224
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ans += data[k] * data[k];226
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}228
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return (ans);230
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}232
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/**235
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* Sums the squares of all components;237
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* also called the energy of the array.239
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*/241
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public static double sumSquares(double[][] data) {243
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double ans = 0.0;245
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for (int k = 0; k < data.length; k++) {247
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for (int l = 0; l < data[k].length; l++) {249
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ans += data[k][l] * data[k][l];251
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}253
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}255
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