使用Java实现K-Means聚类算法

版权声明：啊 这是啥 https://blog.csdn.net/huangyueranbbc/article/details/79425836

第一次写博客，随便写写。

关于K-Means介绍很多，还不清楚可以查一些相关资料。

个人对其实现步骤简单总结为4步:

1.选出k值,随机出k个起始质心点。 
 
2.分别计算每个点和k个起始质点之间的距离,就近归类。 
 
3.最终中心点集可以划分为k类,分别计算每类中新的中心点。 
 

4.重复2,3步骤对所有点进行归类,如果当所有分类的质心点不再改变,则最终收敛。

下面贴代码。

1.入口类，基本读取数据源进行训练然后输出。 数据源文件和源码后面会补上。

package com.hyr.kmeans;

import au.com.bytecode.opencsv.CSVReader;

import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class KmeansMain {

    public static void main(String[] args) throws IOException {
        // 读取数据源文件
        CSVReader reader = new CSVReader(new FileReader("src/main/resources/data.csv")); // 数据源
        FileWriter writer = new FileWriter("src/main/resources/out.csv");
        List<String[]> myEntries = reader.readAll(); // 6.8, 12.6

        // 转换数据点集
        List<Point> points = new ArrayList<Point>(); // 数据点集
        for (String[] entry : myEntries) {
            points.add(new Point(Float.parseFloat(entry[0]), Float.parseFloat(entry[1])));
        }

        int k = 6; // K值
        int type = 1;
        KmeansModel model = Kmeans.run(points, k, type);

        writer.write("====================   K is " + model.getK() + " ,  Object Funcion Value is " + model.getOfv() + " ,  calc_distance_type is " + model.getCalc_distance_type() + "   ====================\n");
        int i = 0;
        for (Cluster cluster : model.getClusters()) {
            i++;
            writer.write("====================   classification " + i + "   ====================\n");
            for (Point point : cluster.getPoints()) {
                writer.write(point.toString() + "\n");
            }
            writer.write("\n");
            writer.write("centroid is " + cluster.getCentroid().toString());
            writer.write("\n\n");
        }

        writer.close();

    }

}

2.最终生成的模型类,也就是最终训练好的结果。K值,计算的点距离类型以及object function value值。

package com.hyr.kmeans;

import java.util.ArrayList;
import java.util.List;

public class KmeansModel {

    private List<Cluster> clusters = new ArrayList<Cluster>();
    private Double ofv;
    private int k;  // k值
    private int calc_distance_type;

    public KmeansModel(List<Cluster> clusters, Double ofv, int k, int calc_distance_type) {
        this.clusters = clusters;
        this.ofv = ofv;
        this.k = k;
        this.calc_distance_type = calc_distance_type;
    }

    public List<Cluster> getClusters() {
        return clusters;
    }

    public Double getOfv() {
        return ofv;
    }

    public int getK() {
        return k;
    }

    public int getCalc_distance_type() {
        return calc_distance_type;
    }
}

3.数据集点对象,包含点的维度,代码里只给出了x轴,y轴二维。以及点的距离计算。通过类型选择距离公式。给出了几种常用的距离公式。

package com.hyr.kmeans;

public class Point {

    private Float x;     // x 轴
    private Float y;    // y 轴

    public Point(Float x, Float y) {
        this.x = x;
        this.y = y;
    }

    public Float getX() {
        return x;
    }

    public void setX(Float x) {
        this.x = x;
    }

    public Float getY() {
        return y;
    }

    public void setY(Float y) {
        this.y = y;
    }

    @Override
    public String toString() {
        return "Point{" +
                "x=" + x +
                ", y=" + y +
                '}';
    }

    /**
     * 计算距离
     *
     * @param centroid 质心点
     * @param type
     * @return
     */
    public Double calculateDistance(Point centroid, int type) {
        // TODO
        Double result = null;
        switch (type) {
            case 1:
                result = calcL1Distance(centroid);
                break;
            case 2:
                result = calcCanberraDistance(centroid);
                break;
            case 3:
                result = calcEuclidianDistance(centroid);
                break;
        }
        return result;
    }



    /*
            计算距离公式
     */

    private Double calcL1Distance(Point centroid) {
        double res = 0;
        res = Math.abs(getX() - centroid.getX()) + Math.abs(getY() - centroid.getY());
        return res / (double) 2;
    }

    private double calcEuclidianDistance(Point centroid) {
        return Math.sqrt(Math.pow((centroid.getX() - getX()), 2) + Math.pow((centroid.getY() - getY()), 2));
    }

    private double calcCanberraDistance(Point centroid) {
        double res = 0;
        res = Math.abs(getX() - centroid.getX()) / (Math.abs(getX()) + Math.abs(centroid.getX()))
                + Math.abs(getY() - centroid.getY()) / (Math.abs(getY()) + Math.abs(centroid.getY()));
        return res / (double) 2;
    }

    @Override
    public boolean equals(Object obj) {
        Point other = (Point) obj;
        if (getX().equals(other.getX()) && getY().equals(other.getY())) {
            return true;
        }
        return false;
    }
}

4.训练后最终得到的分类。包含该分类的质点,属于该分类的点集合该分类是否收敛。

package com.hyr.kmeans;

import java.util.ArrayList;
import java.util.List;

public class Cluster {

    private List<Point> points = new ArrayList<Point>(); // 属于该分类的点集
    private Point centroid; // 该分类的中心质点
    private boolean isConvergence = false;

    public Point getCentroid() {
        return centroid;
    }

    public void setCentroid(Point centroid) {
        this.centroid = centroid;
    }

    @Override
    public String toString() {
        return centroid.toString();
    }

    public List<Point> getPoints() {
        return points;
    }

    public void setPoints(List<Point> points) {
        this.points = points;
    }


    public void initPoint() {
        points.clear();
    }

    public boolean isConvergence() {
        return isConvergence;
    }

    public void setConvergence(boolean convergence) {
        isConvergence = convergence;
    }
}

5.K-Meams训练类。按照上面所说四个步骤不断进行训练。

package com.hyr.kmeans;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class Kmeans {

    /**
     * kmeans
     *
     * @param points 数据集
     * @param k      K值
     * @param k      计算距离方式
     */
    public static KmeansModel run(List<Point> points, int k, int type) {
        // 初始化质心点
        List<Cluster> clusters = initCentroides(points, k);

        while (!checkConvergence(clusters)) { // 所有分类是否全部收敛
            // 1.计算距离对每个点进行分类
            // 2.判断质心点是否改变,未改变则该分类已经收敛
            // 3.重新生成质心点
            initClusters(clusters); // 重置分类中的点
            classifyPoint(points, clusters, type);// 计算距离进行分类
            recalcularCentroides(clusters); // 重新计算质心点
        }

        // 计算目标函数值
        Double ofv = calcularObjetiFuncionValue(clusters);

        KmeansModel kmeansModel = new KmeansModel(clusters, ofv, k, type);

        return kmeansModel;
    }

    /**
     * 初始化k个质心点
     *
     * @param points 点集
     * @param k      K值
     * @return 分类集合对象
     */
    private static List<Cluster> initCentroides(List<Point> points, Integer k) {
        List<Cluster> centroides = new ArrayList<Cluster>();

        // 求出数据集的范围(找出所有点的x最小、最大和y最小、最大坐标。)
        Float max_X = Float.NEGATIVE_INFINITY;
        Float max_Y = Float.NEGATIVE_INFINITY;
        Float min_X = Float.POSITIVE_INFINITY;
        Float min_Y = Float.POSITIVE_INFINITY;
        for (Point point : points) {
            max_X = max_X < point.getX() ? point.getX() : max_X;
            max_Y = max_Y < point.getY() ? point.getY() : max_Y;
            min_X = min_X > point.getX() ? point.getX() : min_X;
            min_Y = min_Y > point.getY() ? point.getY() : min_Y;
        }
        System.out.println("min_X" + min_X + ",max_X:" + max_X + ",min_Y" + min_Y + ",max_Y" + max_Y);

        // 在范围内随机初始化k个质心点
        Random random = new Random();
        // 随机初始化k个中心点
        for (int i = 0; i < k; i++) {
            float x = random.nextFloat() * (max_X - min_X) + min_X;
            float y = random.nextFloat() * (max_Y - min_Y) + min_X;
            Cluster c = new Cluster();
            Point centroide = new Point(x, y); // 初始化的随机中心点
            c.setCentroid(centroide);
            centroides.add(c);
        }

        return centroides;
    }

    /**
     * 重新计算质心点
     *
     * @param clusters
     */
    private static void recalcularCentroides(List<Cluster> clusters) {
        for (Cluster c : clusters) {
            if (c.getPoints().isEmpty()) {
                c.setConvergence(true);
                continue;
            }

            // 求均值,作为新的质心点
            Float x;
            Float y;
            Float sum_x = 0f;
            Float sum_y = 0f;
            for (Point point : c.getPoints()) {
                sum_x += point.getX();
                sum_y += point.getY();
            }
            x = sum_x / c.getPoints().size();
            y = sum_y / c.getPoints().size();
            Point nuevoCentroide = new Point(x, y); // 新的质心点

            if (nuevoCentroide.equals(c.getCentroid())) { // 如果质心点不再改变 则该分类已经收敛
                c.setConvergence(true);
            } else {
                c.setCentroid(nuevoCentroide);
            }
        }
    }

    /**
     * 计算距离,对点集进行分类
     *
     * @param points   点集
     * @param clusters 分类
     * @param type     计算距离方式
     */
    private static void classifyPoint(List<Point> points, List<Cluster> clusters, int type) {
        for (Point point : points) {
            Cluster masCercano = clusters.get(0); // 该点计算距离后所属的分类
            Double minDistancia = Double.MAX_VALUE; // 最小距离
            for (Cluster cluster : clusters) {
                Double distancia = point.calculateDistance(cluster.getCentroid(), type); // 点和每个分类质心点的距离
                if (minDistancia > distancia) { // 得到该点和k个质心点最小的距离
                    minDistancia = distancia;
                    masCercano = cluster; // 得到该点的分类
                }
            }
            masCercano.getPoints().add(point); // 将该点添加到距离最近的分类中
        }
    }

    private static void initClusters(List<Cluster> clusters) {
        for (Cluster cluster : clusters) {
            cluster.initPoint();
        }
    }

    /**
     * 检查收敛
     *
     * @param clusters
     * @return
     */
    private static boolean checkConvergence(List<Cluster> clusters) {
        for (Cluster cluster : clusters) {
            if (!cluster.isConvergence()) {
                return false;
            }
        }
        return true;
    }

    /**
     * 计算目标函数值
     *
     * @param clusters
     * @return
     */
    private static Double calcularObjetiFuncionValue(List<Cluster> clusters) {
        Double ofv = 0d;

        for (Cluster cluster : clusters) {
            for (Point point : cluster.getPoints()) {
                int type = 1;
                ofv += point.calculateDistance(cluster.getCentroid(), type);
            }
        }

        return ofv;
    }
}

最终训练结果:

====================   K is 6 ,  Object Funcion Value is 21.82857036590576 ,  calc_distance_type is 3   ====================
====================   classification 1   ====================
Point{x=3.5, y=12.5}

centroid is Point{x=3.5, y=12.5}

====================   classification 2   ====================
Point{x=6.8, y=12.6}
Point{x=7.8, y=12.2}
Point{x=8.2, y=11.1}
Point{x=9.6, y=11.1}

centroid is Point{x=8.1, y=11.75}

====================   classification 3   ====================
Point{x=4.4, y=6.5}
Point{x=4.8, y=1.1}
Point{x=5.3, y=6.4}
Point{x=6.6, y=7.7}
Point{x=8.2, y=4.5}
Point{x=8.4, y=6.9}
Point{x=9.0, y=3.4}

centroid is Point{x=6.671428, y=5.2142863}

====================   classification 4   ====================
Point{x=6.0, y=19.9}
Point{x=6.2, y=18.5}
Point{x=5.3, y=19.4}
Point{x=7.6, y=17.4}

centroid is Point{x=6.275, y=18.800001}

====================   classification 5   ====================
Point{x=0.8, y=9.8}
Point{x=1.2, y=11.6}
Point{x=2.8, y=9.6}
Point{x=3.8, y=9.9}

centroid is Point{x=2.15, y=10.225}

====================   classification 6   ====================
Point{x=6.1, y=14.3}

centroid is Point{x=6.1, y=14.3}

代码下载地址:

http://download.csdn.net/download/huangyueranbbc/10267041

github: 

https://github.com/huangyueranbbc/KmeansDemo