kmeans.java

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

public class Kmeans {

	int numCenter = 3;
	int numPoint = 9;
	int maxIter = 10;
	List<List<Double>> listPoint;
	List<List<Double>> listCenter;
	List<List<Integer>> listCluster;
	
	
	public static void main(String[] args) {

		Kmeans kmeans = new Kmeans();
		kmeans.initPoint();
		kmeans.initCenterAndCluster();
		
		int i = 0;
		System.out.println("----- Begin ----");

		while(i < kmeans.maxIter) {
			System.out.println("Iter  " + i);
			
			for(int j=0; j<kmeans.numPoint; j++) {
				double xPoint = kmeans.listPoint.get(j).get(0);
				double yPoint = kmeans.listPoint.get(j).get(1);
				
				double distance =  999999999;
				int iCenter = 0;
				for(int k=0; k<kmeans.numCenter; k++) {
					double xCenter = kmeans.listCenter.get(k).get(0);
					double yCenter = kmeans.listCenter.get(k).get(1);					
					double newDistance = Math.sqrt(Math.pow((xPoint-xCenter), 2) + Math.pow((yPoint-yCenter), 2));
					if(distance > newDistance) {
						distance = newDistance;
						iCenter = k;
					}
				}
				kmeans.listCluster.get(iCenter).add(j);
			}
			
			for(int m=0; m<kmeans.numCenter; m++) {
				int s = kmeans.listCluster.get(m).size();
				
				double xPointSum = 0.0;
				double yPointSum = 0.0;
				
				for(int n=0; n<s; n++) {
					 int iPoint = kmeans.listCluster.get(m).get(n);
					 double xPoint = kmeans.listPoint.get(iPoint).get(0);
					 double yPoint = kmeans.listPoint.get(iPoint).get(1);
					 xPointSum = xPointSum + xPoint;
					 yPointSum = yPointSum + yPoint;
				}
				double xPointCenterNew  = xPointSum/s;
				double yPointCenterNew  = yPointSum/s;
				kmeans.listCenter.get(m).set(0, xPointCenterNew);
				kmeans.listCenter.get(m).set(1, yPointCenterNew);

			}
			
			for(int m=0; m<kmeans.numCenter; m++) {
				int s = kmeans.listCluster.get(m).size();
				System.out.print(" Cluster " +  m + ": ");		
				for(int z=0; z<s; z++) { 
					int index = kmeans.listCluster.get(m).get(z);
					System.out.print(index + " ");
				}	
				
				double xPointCenter  = kmeans.listCenter.get(m).get(0);
				double yPointCenter  = kmeans.listCenter.get(m).get(1);
				
				System.out.print("PointCenter " + m + ": (" + xPointCenter + "," +yPointCenter + ")" );
				System.out.print("\n");
			
			}
			
	
			
			for(int p=0; p<kmeans.numCenter; p++) {
				kmeans.listCluster.get(p).clear();
			}
			i++;
		}
		System.out.println("----- End ----");

		
	}
	

	public void initPoint() {
		
		
		listPoint = new ArrayList<List<Double>>();
		listCenter = new ArrayList<List<Double>>();
		listCluster = new ArrayList<List<Integer>>();
		
	
		List<Double> listP0 =  new  ArrayList<Double>();
		listP0.add(2.0);
		listP0.add(5.0);
		
		List<Double> listP1 =  new  ArrayList<Double>();
		listP1.add(5.0);
		listP1.add(10.0);
		
		List<Double> listP2 =  new  ArrayList<Double>();
		listP2.add(1.0);
		listP2.add(7.0);
		
		List<Double> listP3 =  new  ArrayList<Double>();
		listP3.add(5.0);
		listP3.add(8.0);
		
		List<Double> listP4 =  new  ArrayList<Double>();
		listP4.add(1.0);
		listP4.add(1.0);
		
		List<Double> listP5 =  new  ArrayList<Double>();
		listP5.add(1.0);
		listP5.add(1.0);
		
		List<Double> listP6 =  new  ArrayList<Double>();
		listP6.add(1.0);
		listP6.add(9.0);
		
		
		List<Double> listP7 =  new  ArrayList<Double>();
		listP7.add(3.0);
		listP7.add(3.0);
		
		
		List<Double> listP8 =  new  ArrayList<Double>();
		listP8.add(5.0);
		listP8.add(5.0);
		
		
		listPoint.add(listP0);
		listPoint.add(listP1);
		listPoint.add(listP2);
		listPoint.add(listP3);
		listPoint.add(listP4);
		listPoint.add(listP5);
		listPoint.add(listP6);
		listPoint.add(listP7);
		listPoint.add(listP8);

	}

	public void initCenterAndCluster() {
		
		listCenter.add(listPoint.get(0));
		listCenter.add(listPoint.get(1));
		listCenter.add(listPoint.get(2));
		
		listCluster.add(new ArrayList<>());
		listCluster.add(new ArrayList<>());
		listCluster.add(new ArrayList<>());
			
	}
}