文章目录

  • 说明
  • Day51-52 KNN 分类器
    • 1.KNN
    • 2.代码
      • 1.aff内容解读
      • 2.代码理解
  • Day53 knn补充
    • 1.加权思路
    • 2.加权代码
    • 3.leave-one-out 测试思路
    • 4.leave-one-out代码

说明

闵老师的文章链接： 日撸 Java 三百行（总述）_minfanphd的博客-CSDN博客
自己也把手敲的代码放在了github上维护：https://github.com/fulisha-ok/sampledata

Day51-52 KNN 分类器

今天开始学习机器学习，这是自己之前未接触过的，若在理解过程中有问题，欢迎批评指正~

1.KNN

正如物以类聚，人以群居。越是相似的东西就越有可能是一类东西。从这张图片来看，判断Xu属于那种类别，可以取Xu最近的K个邻居（距离），在这个K个点中，那一类东西的概率最高，就把他定位为那个类别。其中计算距离的方式有两种：

欧式距离(多维空间)： d = ∑ i = 1 n ( x i − x j ) 2 d = \sqrt{{\sum_{i=1}^{n}}(x _{i}-x _{j} ) ^2} d=i=1∑n​(xi​−xj​)2 ​
曼哈顿距离： d = ∣ x 1 − x 2 ∣ + ∣ y 1 − y 2 ∣ d = \mid x1 -x2 \mid + \mid y1 -y2 \mid d=∣x1−x2∣+∣y1−y2∣

KNN算法最简单粗暴的就是将预测点与所有点距离进行计算，然后保存并排序，选出前面K个值看看哪些类别比较多。(在电商中，可以根据消费者选择的东西去推荐他们可能感兴趣的的商品，还可以在一些网站可以看到相似用户这些。)

2.代码

在写代码前要导入一个jar包。​下载jar包的网址：https://mvnrepository.com/

1.aff内容解读

在aff文件中有3种类型的花（山鸢尾（Iris-setosa），变色鸢尾（Iris-versicolor），维吉尼亚鸢尾（Iris-virginica）），每一个花类有50个数据，每条记录有 4 项特征（花萼长度、花萼宽度、花瓣长度、花瓣宽度）

2.代码理解

  • 解析文本内容，获取数据集
  • 根据获取的数据集划分训练集和测试集,对获取的数据集先打乱数据索引位置再进行分割，以保证在取数时更有说服性trainingSet(代码中是分了120个数据集)和testingSet(30个训练集)
  • 对测试集数据进行遍历预测：对每一个测试数据，计算他到所有训练集的距离，取他的k个邻居，这k个邻居是距离这个测试数据最近得k个点（代码中计算距离用的欧式距离）
  • 取出测试集的预测结果与数据集中的结果进行比较，判断预测正确率
package machinelearing.knn;import weka.core.Instance;
import weka.core.Instances;import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Arrays;
import java.util.Random;/*** @author： fulisha* @date： 2023/5/15 9:43* @description：*/
public class KnnClassification {/*** Manhattan distance.*/public static final int MANHATTAN = 0;/*** Euclidean distance(欧几里得距离)*/public static final int EUCLIDEAN = 1;/*** The distance measure*/public int distanceMeasure = EUCLIDEAN;/*** a random instance*/public static final Random random = new Random();/*** The number of neighbors*/int numNeighbors = 7;/*** The whole dataset*/Instances dataset;/***  The training set. Represented by the indices of the data*/int[] trainingSet;/*** The testing set. Represented by the indices of the data.*/int[] testingSet;/*** the predictions*/int[] predictions;public void setDistanceMeasure(int distanceMeasure) {this.distanceMeasure = distanceMeasure;}public void setNumNeighbors(int numNeighbors) {this.numNeighbors = numNeighbors;}/*** the first constructor* @param paraFilename The arff filename.*/public KnnClassification(String paraFilename) {try {FileReader fileReader  = new FileReader(paraFilename);dataset = new Instances(fileReader);// the last attribute is the decision classdataset.setClassIndex(dataset.numAttributes() - 1);fileReader.close();} catch (Exception e) {System.out.println("Error occurred while trying to read \'" + paraFilename + "\' in KnnClassification constructor.\r\n" + e);System.exit(0);}}/*** get a random indices for data randomization* @param paraLength the length of the sequence* @return An array of indices. eg.{4, 3, 1, 5, 0, 2} with length 6*/public static int[] getRandomIndices(int paraLength) {int[] resultIndices = new int[paraLength];//step1. Initializefor (int i = 0; i < paraLength; i++) {resultIndices[i] = i;}//step2 Randomly swapint tempFirst, tempSecond, tempValue;for (int i = 0; i < paraLength; i++) {//Generate two random indicestempFirst =  random.nextInt(paraLength);tempSecond = random.nextInt(paraLength);//swaptempValue = resultIndices[tempFirst];resultIndices[tempFirst] = resultIndices[tempSecond];resultIndices[tempSecond] = tempValue;}return resultIndices;}public void splitTrainingTesting(double paraTrainingFraction) {int tempSize = dataset.numInstances();int[] tempIndices = getRandomIndices(tempSize);int tempTrainingSize = (int) (tempSize * paraTrainingFraction);trainingSet = new int[tempTrainingSize];testingSet = new int[tempSize - tempTrainingSize];for (int i = 0; i < tempTrainingSize; i++) {trainingSet[i] = tempIndices[i];}for (int i = 0; i < tempSize - tempTrainingSize; i++) {testingSet[i] = tempIndices[tempTrainingSize + i];}}/*** Predict for the whole testing set. The results are stored in predictions*/public void predict() {predictions = new int[testingSet.length];for (int i = 0; i < predictions.length; i++) {predictions[i] = predict(testingSet[i]);}}/*** Predict for given instance* @param paraIndex* @return*/public int predict(int paraIndex) {int[] tempNeighbors = computeNearests(paraIndex);int resultPrediction = simpleVoting(tempNeighbors);return resultPrediction;}/*** The distance between two instance* @param paraI The index of the first instance* @param paraJ The index of the second instance* @return The distance*/public double distance(int paraI, int paraJ) {double resultDistance = 0;double tempDifference;switch (distanceMeasure) {case MANHATTAN:for (int i = 0; i < dataset.numAttributes() - 1; i++) {tempDifference = dataset.instance(paraI).value(i) - dataset.instance(paraJ).value(i);if (tempDifference < 0) {resultDistance -= tempDifference;}else {resultDistance += tempDifference;}}break;case EUCLIDEAN:for (int i = 0; i < dataset.numAttributes() - 1; i++) {tempDifference = dataset.instance(paraI).value(i) - dataset.instance(paraJ).value(i);resultDistance += tempDifference*tempDifference;}break;default:System.out.println("Unsupported distance measure: " + distanceMeasure);}return resultDistance;}/*** Get the accuracy of the classifier* @return*/public double getAccuracy() {// A double divides an int gets another doubledouble tempCorrect = 0;for (int i = 0; i < predictions.length; i++) {if (predictions[i] == dataset.instance(testingSet[i]).classValue()) {tempCorrect++;}}return tempCorrect / testingSet.length;}/*** compute the nearnest k neighbors.select one neighbor in each scan.* @param paraCurrent* @return*/public int[] computeNearests(int paraCurrent) {int[] resultNearests = new int[numNeighbors];boolean[] tempSelected = new boolean[trainingSet.length];double tempMinimalDistance;int tempMinimalIndex = 0;//compute all distance to avoid redundant computationdouble[] tempDistances = new double[trainingSet.length];for (int i = 0; i < trainingSet.length; i ++) {tempDistances[i] = distance(paraCurrent, trainingSet[i]);}// Select the nearest paraK indices.for (int i = 0; i < numNeighbors; i++) {tempMinimalDistance = Double.MAX_VALUE;for (int j = 0; j < trainingSet.length; j++) {if (tempSelected[j]) {continue;}if (tempDistances[j] < tempMinimalDistance) {tempMinimalDistance = tempDistances[j];tempMinimalIndex = j;}}resultNearests[i] = trainingSet[tempMinimalIndex];tempSelected[tempMinimalIndex] = true;}System.out.println("The nearest of " + paraCurrent + " are: " + Arrays.toString(resultNearests));return resultNearests;}/*** Voting using the instances* @param paraNeighbors The indices of the neighbors.* @return The predicted label.*/public int simpleVoting(int[] paraNeighbors) {int[] tempVotes = new int[dataset.numClasses()];for (int i = 0; i < paraNeighbors.length; i++) {tempVotes[(int) dataset.instance(paraNeighbors[i]).classValue()]++;}int tempMaximalVotingIndex = 0;int tempMaximalVoting = 0;for (int i = 0; i < dataset.numClasses(); i++) {if (tempVotes[i] > tempMaximalVoting) {tempMaximalVoting = tempVotes[i];tempMaximalVotingIndex = i;}}return tempMaximalVotingIndex;}public static void main(String[] args) {KnnClassification tempClassifier = new KnnClassification("D:/fulisha/iris.arff");tempClassifier.splitTrainingTesting(0.8);tempClassifier.predict();System.out.println("The accuracy of the classifier is: " + tempClassifier.getAccuracy());}}

运行结果：

The nearest of 56 are: [51, 91, 127, 86, 70, 138, 63]
The nearest of 11 are: [29, 7, 26, 30, 24, 6, 49]
The nearest of 21 are: [19, 17, 4, 48, 0, 40, 43]
The nearest of 119 are: [72, 68, 146, 113, 123, 101, 142]
The nearest of 12 are: [1, 9, 37, 34, 45, 30, 25]
The nearest of 85 are: [70, 51, 91, 61, 138, 63, 127]
The nearest of 83 are: [101, 142, 149, 123, 127, 72, 138]
The nearest of 103 are: [116, 137, 111, 147, 134, 108, 149]
The nearest of 93 are: [60, 98, 81, 80, 79, 59, 69]
The nearest of 66 are: [84, 55, 96, 61, 95, 88, 94]
The nearest of 104 are: [140, 124, 143, 120, 144, 116, 100]
The nearest of 32 are: [33, 19, 48, 10, 16, 5, 4]
The nearest of 132 are: [111, 140, 116, 147, 115, 137, 145]
The nearest of 90 are: [94, 55, 96, 89, 99, 95, 92]
The nearest of 54 are: [58, 75, 76, 86, 74, 65, 51]
The nearest of 47 are: [42, 6, 29, 45, 30, 9, 37]
The nearest of 136 are: [148, 115, 100, 144, 140, 124, 143]
The nearest of 38 are: [8, 42, 13, 45, 6, 29, 30]
The nearest of 3 are: [29, 30, 45, 42, 8, 9, 37]
The nearest of 129 are: [125, 130, 102, 107, 139, 108, 124]
The nearest of 128 are: [111, 116, 137, 147, 140, 115, 108]
The nearest of 2 are: [6, 45, 42, 29, 1, 35, 9]
The nearest of 133 are: [72, 123, 127, 63, 111, 77, 146]
The nearest of 46 are: [19, 48, 4, 10, 44, 0, 17]
The nearest of 57 are: [98, 60, 81, 80, 59, 79, 69]
The nearest of 126 are: [123, 127, 138, 146, 63, 72, 149]
The nearest of 67 are: [92, 82, 99, 69, 94, 95, 96]
The nearest of 112 are: [139, 140, 120, 145, 124, 116, 147]
The nearest of 78 are: [91, 63, 61, 97, 55, 73, 138]
The nearest of 27 are: [28, 39, 0, 17, 48, 7, 4]
The accuracy of the classifier is: 0.9666666666666667

Day53 knn补充

1.加权思路

距离加权，距离越短说明他们的话语权最大，采用了最简单的方式，采用倒数形式，距离为d，则它的权重为1/d，可以对距离再进行平方，在进行倒数都可以。我这里改进方法是两种

  • 结合我们k个邻居的数组是按距离从小到大来进行排序的，那么我这里可以不用去花一个数组去存储距离，而是用他的索引值i去平替他的距离
  • 我们即用一个对象去存储测试点到这k个邻居的距离，当然也可以不存储，那你就得再去算一次，但我觉得牺牲一点空间存储也是可以的。用实际距离去计算权重。（代码中新增了一个 Map<Integer, double[]> distanceMap = new HashMap<>();来全局记录测试点到k个邻居的距离）

2.加权代码

我全局新增三种投票模式 新增一个set方法全局定义一个选择投票的方式

    /*** simple voting*/public static final int VOTE_SIMPLE = 0;/*** add index to simple voting(用索引做距离的平替)*/public static final int VOTE_DISTANCE_1 = 1;/*** add distance to simple voting(actual distance)*/public static final int VOTE_DISTANCE_2 = 2;/*** The vote measure*/public int voteDistance = VOTE_SIMPLE;public void setVoteDistance(Integer vote) {this.voteDistance = vote;}

新增weightedVoting方法替代simpleVoting方法，根据所传参数来选择投票方式。

 public int weightedVoting(int[] paraNeighbors, Integer weightModel, double[] tempDistances) {int[] tempVotes = new int[dataset.numClasses()];for (int i = 0; i < paraNeighbors.length; i++) {//voting 花类型的索引indexint index = (int)dataset.instance(paraNeighbors[i]).classValue();if (weightModel.equals(VOTE_SIMPLE)) {tempVotes[index]++;} else if (weightModel.equals(VOTE_DISTANCE_1)) {// 因为本身paraNeighbors存储的顺序是按从小到大的顺序存储的，我用i做平替tempVotes[index] += 1/(i+1);} else if (weightModel.equals(VOTE_DISTANCE_2)) {// 用具体的距离方式tempVotes[index] += 1/tempDistances[i];}}int tempMaximalVotingIndex = 0;int tempMaximalVoting = 0;for (int i = 0; i < dataset.numClasses(); i++) {if (tempVotes[i] > tempMaximalVoting) {tempMaximalVoting = tempVotes[i];tempMaximalVotingIndex = i;}}return tempMaximalVotingIndex;}

3.leave-one-out 测试思路

  • 将数据集中的每一个样本都被单独作为测试集，而剩下的样本就作为训练集。就像我们的代码中，我们一共有150个数据集，我们依次将样本作为测试集，而剩下的149个样本就作为训练集，在每一次的迭代中，每次选择一个不同的样本作为测试集，直到所有样本都被用作测试集为止。（不同的投票方式结果不一样）

4.leave-one-out代码

  • 主要代码如下：（数据集我是打乱了顺序，其实不打乱顺序也无所谓，不会影响结果）
/*** leave-one-out test*/public void leaveOneOutTesting() {int tempSize = dataset.numInstances();//int[] predicts = new int[tempSize];int[] tempIndices = getRandomIndices(tempSize);int tempCorrect = 0;for (int i = 0; i < tempSize; i++) {// 分训练集和测试集 （测试集一个.其余为训练集）splitByIndex(tempIndices, i);int[] neighbors = computeNearests(tempIndices[i]);int resultPrediction = weightedVoting(neighbors, voteDistance, distanceMap.get(tempIndices[i]));if(resultPrediction == dataset.instance(tempIndices[i]).classValue()){tempCorrect++;} else{System.out.println(tempIndices[i] + "The resultPrediction " + resultPrediction + " and actual result " + dataset.instance(tempIndices[i]).classValue());}}System.out.println("The total size " + tempSize + ", after leave-one-test, the correct predict size :" + tempCorrect);}/*** split for leave-one-out test* @param tempIndices the given dataSet* @param index the index*/public void splitByIndex(int[] tempIndices, int index) {int tempSize = dataset.numInstances();int tempTrainingSize  = tempSize - 1;testingSet = new int[1];trainingSet = new int[tempTrainingSize];testingSet[0]  = tempIndices[index];int j = 0;for (int i = 0; i < tempSize; i++) {if (i == index) {continue;}trainingSet[j++] = tempIndices[i];}}

运行结果

The nearest of 14 are: [33, 16, 15, 18, 10, 36, 48]
The nearest of 70 are: [138, 127, 149, 85, 56, 126, 91]
70 The resultPrediction 2 and actual result 1.0
The nearest of 3 are: [47, 29, 30, 2, 45, 12, 38]
The nearest of 95 are: [96, 88, 99, 94, 61, 55, 67]
The nearest of 19 are: [21, 46, 48, 4, 17, 0, 27]
The nearest of 90 are: [94, 55, 96, 89, 99, 67, 95]
The nearest of 6 are: [47, 2, 11, 42, 29, 3, 30]
The nearest of 56 are: [51, 85, 91, 127, 86, 70, 138]
The nearest of 4 are: [0, 17, 40, 7, 39, 27, 19]
The nearest of 12 are: [1, 34, 37, 9, 45, 30, 2]
The nearest of 48 are: [10, 27, 19, 46, 21, 0, 17]
The nearest of 75 are: [65, 58, 74, 54, 51, 86, 97]
The nearest of 39 are: [7, 0, 28, 27, 49, 17, 26]
The nearest of 49 are: [7, 39, 35, 0, 28, 17, 40]
The nearest of 142 are: [101, 113, 121, 149, 83, 127, 138]
The nearest of 43 are: [26, 23, 21, 17, 40, 7, 39]
The nearest of 124 are: [120, 143, 112, 140, 104, 144, 139]
The nearest of 17 are: [0, 40, 4, 39, 28, 27, 7]
The nearest of 68 are: [87, 72, 119, 54, 73, 146, 123]
The nearest of 34 are: [37, 9, 1, 30, 12, 25, 49]
The nearest of 118 are: [122, 105, 135, 107, 130, 117, 102]
The nearest of 37 are: [34, 9, 1, 30, 12, 25, 49]
The nearest of 21 are: [19, 46, 17, 4, 48, 0, 27]
The nearest of 8 are: [38, 3, 42, 13, 47, 12, 45]
The nearest of 24 are: [11, 29, 26, 30, 7, 23, 39]
The nearest of 108 are: [128, 103, 132, 116, 111, 112, 104]
The nearest of 122 are: [105, 118, 107, 130, 135, 125, 117]
The nearest of 104 are: [132, 128, 140, 124, 143, 112, 120]
The nearest of 115 are: [148, 110, 145, 147, 136, 140, 132]
The nearest of 35 are: [49, 1, 2, 40, 28, 34, 37]
The nearest of 92 are: [82, 67, 99, 69, 94, 89, 71]
The nearest of 119 are: [72, 83, 68, 146, 113, 123, 133]
119 The resultPrediction 1 and actual result 2.0
The nearest of 61 are: [96, 78, 95, 99, 88, 97, 71]
The nearest of 102 are: [125, 120, 143, 130, 112, 129, 124]
The nearest of 45 are: [1, 12, 30, 2, 3, 34, 37]
The nearest of 127 are: [138, 126, 149, 70, 123, 83, 133]
The nearest of 106 are: [84, 59, 90, 89, 94, 66, 53]
106 The resultPrediction 1 and actual result 2.0
The nearest of 22 are: [6, 2, 40, 42, 47, 4, 35]
The nearest of 93 are: [57, 60, 98, 81, 80, 79, 59]
The nearest of 18 are: [5, 10, 48, 20, 16, 31, 36]
The nearest of 130 are: [107, 102, 125, 129, 135, 105, 122]
The nearest of 98 are: [57, 93, 60, 79, 81, 80, 64]
The nearest of 36 are: [10, 31, 28, 48, 27, 0, 20]
The nearest of 0 are: [17, 4, 39, 28, 27, 40, 7]
The nearest of 32 are: [33, 46, 19, 48, 10, 5, 16]
The nearest of 33 are: [32, 15, 16, 14, 5, 10, 48]
The nearest of 2 are: [47, 3, 6, 12, 45, 42, 29]
The nearest of 57 are: [93, 98, 60, 81, 80, 59, 79]
The nearest of 125 are: [129, 102, 107, 130, 143, 120, 124]
The nearest of 13 are: [38, 42, 8, 47, 2, 3, 12]
The nearest of 101 are: [142, 113, 121, 149, 83, 127, 138]
The nearest of 11 are: [29, 7, 26, 24, 30, 6, 49]
The nearest of 73 are: [63, 91, 78, 97, 55, 72, 54]
The nearest of 28 are: [27, 39, 0, 17, 49, 7, 40]
The nearest of 137 are: [116, 103, 147, 128, 111, 110, 112]
The nearest of 55 are: [66, 90, 96, 94, 78, 95, 99]
The nearest of 25 are: [34, 37, 9, 1, 30, 12, 45]
The nearest of 47 are: [3, 2, 42, 6, 29, 38, 12]
The nearest of 91 are: [63, 78, 73, 97, 51, 56, 74]
The nearest of 53 are: [89, 80, 69, 81, 92, 94, 90]
The nearest of 112 are: [139, 140, 120, 145, 124, 116, 104]
The nearest of 44 are: [46, 5, 21, 19, 43, 48, 26]
The nearest of 99 are: [96, 94, 88, 95, 92, 82, 67]
The nearest of 29 are: [30, 3, 11, 47, 34, 37, 9]
The nearest of 132 are: [128, 104, 103, 111, 112, 140, 116]
The nearest of 141 are: [145, 139, 112, 110, 147, 115, 140]
The nearest of 136 are: [148, 115, 100, 144, 140, 124, 104]
The nearest of 138 are: [127, 70, 126, 149, 123, 78, 63]
The nearest of 107 are: [130, 125, 105, 102, 129, 122, 135]
The nearest of 109 are: [143, 120, 144, 102, 135, 124, 125]
The nearest of 88 are: [95, 96, 99, 94, 61, 82, 66]
The nearest of 114 are: [121, 142, 101, 113, 149, 127, 138]
The nearest of 46 are: [19, 21, 48, 4, 27, 10, 32]
The nearest of 149 are: [127, 138, 142, 101, 70, 83, 121]
The nearest of 50 are: [52, 86, 65, 76, 58, 75, 77]
The nearest of 135 are: [130, 105, 102, 107, 122, 125, 109]
The nearest of 147 are: [110, 111, 116, 145, 115, 137, 77]
The nearest of 100 are: [136, 144, 104, 143, 140, 124, 148]
The nearest of 40 are: [17, 0, 4, 7, 49, 39, 28]
The nearest of 133 are: [83, 72, 123, 126, 127, 63, 111]
133 The resultPrediction 1 and actual result 2.0
The nearest of 80 are: [81, 69, 53, 89, 92, 79, 82]
The nearest of 54 are: [58, 75, 76, 86, 74, 65, 51]
The nearest of 82 are: [92, 99, 67, 69, 71, 94, 89]
The nearest of 5 are: [18, 10, 48, 44, 19, 46, 16]
The nearest of 74 are: [97, 75, 58, 54, 65, 51, 71]
The nearest of 85 are: [56, 70, 51, 91, 78, 61, 138]
The nearest of 86 are: [52, 65, 58, 50, 75, 76, 77]
The nearest of 38 are: [8, 42, 13, 3, 47, 2, 45]
The nearest of 87 are: [68, 72, 62, 54, 97, 74, 73]
The nearest of 97 are: [74, 71, 91, 78, 61, 63, 75]
The nearest of 128 are: [132, 104, 103, 111, 116, 137, 112]
The nearest of 139 are: [112, 145, 141, 120, 140, 124, 147]
The nearest of 31 are: [20, 28, 27, 36, 17, 10, 39]
The nearest of 64 are: [82, 79, 88, 99, 69, 59, 92]
The nearest of 134 are: [103, 83, 133, 111, 116, 137, 119]
The nearest of 60 are: [93, 57, 81, 80, 98, 53, 69]
The nearest of 66 are: [84, 55, 96, 78, 61, 95, 88]
The nearest of 77 are: [52, 86, 147, 110, 76, 133, 123]
The nearest of 41 are: [8, 38, 45, 13, 12, 1, 3]
The nearest of 126 are: [123, 127, 138, 146, 83, 133, 63]
The nearest of 89 are: [53, 69, 80, 94, 92, 99, 59]
The nearest of 103 are: [116, 137, 128, 111, 132, 147, 104]
The nearest of 63 are: [91, 73, 78, 97, 138, 126, 54]
The nearest of 10 are: [48, 27, 36, 19, 46, 5, 16]
The nearest of 111 are: [147, 128, 146, 103, 116, 123, 132]
The nearest of 105 are: [122, 107, 135, 118, 130, 125, 117]
The nearest of 146 are: [123, 111, 126, 72, 83, 133, 142]
The nearest of 71 are: [97, 82, 92, 61, 99, 74, 67]
The nearest of 79 are: [81, 80, 69, 64, 82, 92, 67]
The nearest of 69 are: [80, 89, 81, 92, 82, 53, 67]
The nearest of 110 are: [147, 115, 77, 145, 137, 116, 141]
The nearest of 78 are: [91, 63, 61, 97, 55, 73, 66]
The nearest of 9 are: [34, 37, 1, 30, 12, 25, 49]
The nearest of 59 are: [89, 94, 53, 80, 69, 88, 64]
The nearest of 145 are: [141, 147, 139, 112, 115, 140, 110]
The nearest of 148 are: [136, 115, 110, 147, 140, 137, 124]
The nearest of 116 are: [137, 103, 147, 111, 128, 112, 132]
The nearest of 16 are: [10, 48, 33, 19, 5, 21, 36]
The nearest of 58 are: [75, 54, 65, 76, 86, 74, 51]
The nearest of 96 are: [95, 99, 88, 94, 61, 55, 92]
The nearest of 23 are: [26, 43, 39, 7, 31, 17, 27]
The nearest of 121 are: [142, 101, 113, 149, 114, 138, 70]
The nearest of 72 are: [133, 123, 146, 83, 119, 126, 54]
72 The resultPrediction 2 and actual result 1.0
The nearest of 123 are: [126, 146, 127, 72, 133, 83, 111]
The nearest of 30 are: [29, 34, 37, 9, 3, 25, 45]
The nearest of 42 are: [38, 47, 3, 2, 6, 8, 13]
The nearest of 113 are: [142, 101, 121, 114, 83, 149, 146]
The nearest of 20 are: [31, 27, 28, 10, 39, 48, 36]
The nearest of 26 are: [23, 43, 7, 39, 17, 11, 49]
The nearest of 84 are: [66, 55, 96, 88, 94, 95, 90]
The nearest of 62 are: [92, 69, 67, 80, 82, 53, 87]
The nearest of 131 are: [117, 105, 135, 109, 125, 122, 107]
The nearest of 143 are: [120, 124, 144, 140, 104, 102, 112]
The nearest of 51 are: [56, 75, 65, 86, 91, 74, 58]
The nearest of 94 are: [99, 96, 90, 89, 88, 92, 55]
The nearest of 117 are: [131, 105, 109, 135, 122, 125, 107]
The nearest of 83 are: [133, 142, 101, 149, 123, 127, 72]
83 The resultPrediction 2 and actual result 1.0
The nearest of 120 are: [143, 140, 124, 144, 112, 139, 102]
The nearest of 67 are: [92, 82, 99, 69, 94, 95, 96]
The nearest of 81 are: [80, 69, 79, 53, 89, 92, 82]
The nearest of 15 are: [33, 14, 5, 16, 18, 32, 10]
The nearest of 65 are: [75, 58, 86, 51, 74, 54, 50]
The nearest of 27 are: [28, 39, 0, 17, 48, 7, 4]
The nearest of 1 are: [45, 12, 34, 37, 9, 25, 30]
The nearest of 129 are: [125, 130, 102, 107, 112, 139, 108]
The nearest of 144 are: [140, 120, 143, 124, 136, 104, 100]
The nearest of 140 are: [144, 120, 112, 143, 104, 124, 139]
The nearest of 76 are: [58, 86, 52, 54, 77, 50, 75]
The nearest of 7 are: [39, 49, 0, 17, 26, 4, 11]
The nearest of 52 are: [50, 86, 77, 76, 58, 65, 54]
The total size 150, after leave-one-test, the correct predict size :144

这三天的全部代码：

package machinelearing.knn;import weka.core.Instance;
import weka.core.Instances;import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.*;/*** @author： fulisha* @date： 2023/5/15 9:43* @description：*/
public class KnnClassification {/*** Manhattan distance.*/public static final int MANHATTAN = 0;/*** Euclidean distance(欧几里得距离)*/public static final int EUCLIDEAN = 1;/*** The distance measure*/public int distanceMeasure = EUCLIDEAN;/*** simple voting*/public static final int VOTE_SIMPLE = 0;/*** add index to simple voting(用索引做距离的平替)*/public static final int VOTE_DISTANCE_1 = 1;/*** add distance to simple voting(actual distance)*/public static final int VOTE_DISTANCE_2 = 2;/*** The vote measure*/public int voteDistance = VOTE_DISTANCE_2;/*** a random instance*/public static final Random random = new Random();/*** The number of neighbors*/int numNeighbors = 7;/*** The whole dataset*/Instances dataset;/***  The training set. Represented by the indices of the data*/int[] trainingSet;/*** The testing set. Represented by the indices of the data.*/int[] testingSet;/*** the predictions*/int[] predictions;Map<Integer, double[]> distanceMap = new HashMap<>();public void setDistanceMeasure(int distanceMeasure) {this.distanceMeasure = distanceMeasure;}public void setNumNeighbors(int numNeighbors) {this.numNeighbors = numNeighbors;}public void setVoteDistance(Integer vote) {this.voteDistance = vote;}/*** the first constructor* @param paraFilename The arff filename.*/public KnnClassification(String paraFilename) {try {FileReader fileReader  = new FileReader(paraFilename);dataset = new Instances(fileReader);// the last attribute is the decision classdataset.setClassIndex(dataset.numAttributes() - 1);fileReader.close();} catch (Exception e) {System.out.println("Error occurred while trying to read \'" + paraFilename + "\' in KnnClassification constructor.\r\n" + e);System.exit(0);}}/*** get a random indices for data randomization* @param paraLength the length of the sequence* @return An array of indices. eg.{4, 3, 1, 5, 0, 2} with length 6*/public static int[] getRandomIndices(int paraLength) {int[] resultIndices = new int[paraLength];//step1. Initializefor (int i = 0; i < paraLength; i++) {resultIndices[i] = i;}//step2 Randomly swapint tempFirst, tempSecond, tempValue;for (int i = 0; i < paraLength; i++) {//Generate two random indicestempFirst =  random.nextInt(paraLength);tempSecond = random.nextInt(paraLength);//swaptempValue = resultIndices[tempFirst];resultIndices[tempFirst] = resultIndices[tempSecond];resultIndices[tempSecond] = tempValue;}return resultIndices;}public void splitTrainingTesting(double paraTrainingFraction) {int tempSize = dataset.numInstances();int[] tempIndices = getRandomIndices(tempSize);int tempTrainingSize = (int) (tempSize * paraTrainingFraction);trainingSet = new int[tempTrainingSize];testingSet = new int[tempSize - tempTrainingSize];for (int i = 0; i < tempTrainingSize; i++) {trainingSet[i] = tempIndices[i];}for (int i = 0; i < tempSize - tempTrainingSize; i++) {testingSet[i] = tempIndices[tempTrainingSize + i];}}public void TrainingTesting() {int tempSize = dataset.numInstances();int[] tempIndices = getRandomIndices(tempSize);int testingSize = 1;trainingSet = new int[tempSize - testingSize];testingSet = new int[testingSize];for (int i = 0; i < tempSize - testingSize; i++) {trainingSet[i] = tempIndices[i];}}/*** Predict for the whole testing set. The results are stored in predictions*/public void predict() {predictions = new int[testingSet.length];for (int i = 0; i < predictions.length; i++) {predictions[i] = predict(testingSet[i]);}}/*** Predict for given instance* @param paraIndex* @return*/public int predict(int paraIndex) {int[] tempNeighbors = computeNearests(paraIndex);//int resultPrediction = simpleVoting(tempNeighbors);int resultPrediction = weightedVoting(tempNeighbors, voteDistance, distanceMap.get(paraIndex));return resultPrediction;}/*** The distance between two instance* @param paraI The index of the first instance* @param paraJ The index of the second instance* @return The distance*/public double distance(int paraI, int paraJ) {double resultDistance = 0;double tempDifference;switch (distanceMeasure) {case MANHATTAN:for (int i = 0; i < dataset.numAttributes() - 1; i++) {tempDifference = dataset.instance(paraI).value(i) - dataset.instance(paraJ).value(i);if (tempDifference < 0) {resultDistance -= tempDifference;}else {resultDistance += tempDifference;}}break;case EUCLIDEAN:for (int i = 0; i < dataset.numAttributes() - 1; i++) {tempDifference = dataset.instance(paraI).value(i) - dataset.instance(paraJ).value(i);resultDistance += tempDifference*tempDifference;}break;default:System.out.println("Unsupported distance measure: " + distanceMeasure);}return resultDistance;}/*** Get the accuracy of the classifier* @return*/public double getAccuracy() {// A double divides an int gets another doubledouble tempCorrect = 0;for (int i = 0; i < predictions.length; i++) {if (predictions[i] == dataset.instance(testingSet[i]).classValue()) {tempCorrect++;}}return tempCorrect / testingSet.length;}/*** compute the nearnest k neighbors.select one neighbor in each scan.* @param paraCurrent* @return*/public int[] computeNearests(int paraCurrent) {int[] resultNearests = new int[numNeighbors];double[] resultDistance = new double[numNeighbors];boolean[] tempSelected = new boolean[trainingSet.length];double tempMinimalDistance;int tempMinimalIndex = 0;//compute all distance to avoid redundant computationdouble[] tempDistances = new double[trainingSet.length];for (int i = 0; i < trainingSet.length; i ++) {tempDistances[i] = distance(paraCurrent, trainingSet[i]);}// Select the nearest paraK indices.for (int i = 0; i < numNeighbors; i++) {tempMinimalDistance = Double.MAX_VALUE;for (int j = 0; j < trainingSet.length; j++) {if (tempSelected[j]) {continue;}if (tempDistances[j] < tempMinimalDistance) {tempMinimalDistance = tempDistances[j];tempMinimalIndex = j;}}resultNearests[i] = trainingSet[tempMinimalIndex];resultDistance[i] = tempDistances[tempMinimalIndex];tempSelected[tempMinimalIndex] = true;}distanceMap.put(paraCurrent, resultDistance);System.out.println("The nearest of " + paraCurrent + " are: " + Arrays.toString(resultNearests));return resultNearests;}/*** Voting using the instances* @param paraNeighbors The indices of the neighbors.* @return The predicted label.*/public int simpleVoting(int[] paraNeighbors) {int[] tempVotes = new int[dataset.numClasses()]; //对k个邻居，看k个邻居种，那种类型的花最多则返回这个类型的花的索引。for (int i = 0; i < paraNeighbors.length; i++) {tempVotes[(int) dataset.instance(paraNeighbors[i]).classValue()]++;}int tempMaximalVotingIndex = 0;int tempMaximalVoting = 0;for (int i = 0; i < dataset.numClasses(); i++) {if (tempVotes[i] > tempMaximalVoting) {tempMaximalVoting = tempVotes[i];tempMaximalVotingIndex = i;}}return tempMaximalVotingIndex;}public int weightedVoting(int[] paraNeighbors, Integer weightModel, double[] tempDistances) {int[] tempVotes = new int[dataset.numClasses()];for (int i = 0; i < paraNeighbors.length; i++) {//voting 花类型的索引indexint index = (int)dataset.instance(paraNeighbors[i]).classValue();if (weightModel.equals(VOTE_SIMPLE)) {tempVotes[index]++;} else if (weightModel.equals(VOTE_DISTANCE_1)) {// 因为本身paraNeighbors存储的顺序是按从小到大的顺序存储的，我用i做平替tempVotes[index] += 1/(i+1);} else if (weightModel.equals(VOTE_DISTANCE_2)) {// 用具体的距离方式tempVotes[index] += 1/tempDistances[i];}}int tempMaximalVotingIndex = 0;int tempMaximalVoting = 0;for (int i = 0; i < dataset.numClasses(); i++) {if (tempVotes[i] > tempMaximalVoting) {tempMaximalVoting = tempVotes[i];tempMaximalVotingIndex = i;}}return tempMaximalVotingIndex;}/*** leave-one-out test*/public void leaveOneOutTesting() {System.out.println("leave one out test ..........................");int tempSize = dataset.numInstances();//int[] predicts = new int[tempSize];int[] tempIndices = getRandomIndices(tempSize);int tempCorrect = 0;for (int i = 0; i < tempSize; i++) {// 分训练集和测试集 （测试集一个.其余为训练集）splitByIndex(tempIndices, i);int[] neighbors = computeNearests(tempIndices[i]);int resultPrediction = weightedVoting(neighbors, voteDistance, distanceMap.get(tempIndices[i]));if(resultPrediction == dataset.instance(tempIndices[i]).classValue()){tempCorrect++;} else{System.out.println(tempIndices[i] + " The resultPrediction " + resultPrediction + " and actual result " + dataset.instance(tempIndices[i]).classValue());}}System.out.println("The total size " + tempSize + ", after leave-one-test, the correct predict size :" + tempCorrect);}/*** split for leave-one-out test* @param tempIndices the given dataSet* @param index the index*/public void splitByIndex(int[] tempIndices, int index) {int tempSize = dataset.numInstances();int tempTrainingSize  = tempSize - 1;testingSet = new int[1];trainingSet = new int[tempTrainingSize];testingSet[0]  = tempIndices[index];int j = 0;for (int i = 0; i < tempSize; i++) {if (i == index) {continue;}trainingSet[j++] = tempIndices[i];}}public static void main(String[] args) {KnnClassification tempClassifier = new KnnClassification("C:/Users/王忠云/Desktop/iris.arff");tempClassifier.leaveOneOutTesting();tempClassifier.splitTrainingTesting(0.8);tempClassifier.predict();System.out.println("The accuracy of the classifier is: " + tempClassifier.getAccuracy());}}

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