programming-examples/java/Implementation of clustering algorithm K-means.java

import java.util.*;
class k_means
{
    static int count1,count2,count3;
    static int d[];
    static int k[][];
    static int tempk[][];
    static double m[];
    static double diff[];
    static int n,p;
    static int cal_diff(int a) // This method will determine the cluster in which an element go at a particular step.
    {
        int temp1=0;
        for(int i=0; i<p; ++i)
            {
                if(a>m[i])
                    diff[i]=a-m[i];
                else
                    diff[i]=m[i]-a;
            }
        int val=0;
        double temp=diff[0];
        for(int i=0; i<p; ++i)
            {
                if(diff[i]<temp)
                    {
                        temp=diff[i];
                        val=i;
                    }
            }//end of for loop
        return val;
    }
    static void cal_mean() // This method will determine intermediate mean values
    {
        for(int i=0; i<p; ++i)
            m[i]=0; // initializing means to 0
        int cnt=0;
        for(int i=0; i<p; ++i)
            {
                cnt=0;
                for(int j=0; j<n-1; ++j)
                    {
                        if(k[i][j]!=-1)
                            {
                                m[i]+=k[i][j];
                                ++cnt;
                            }
                    }
                m[i]=m[i]/cnt;
            }
    }
    static int check1() // This checks if previous k ie. tempk and current k are same.Used as terminating case.
    {
        for(int i=0; i<p; ++i)
            for(int j=0; j<n; ++j)
                if(tempk[i][j]!=k[i][j])
                    {
                        return 0;
                    }
        return 1;
    }
    public static void main(String args[])
    {
        Scanner scr=new Scanner(System.in);
        /* Accepting number of elements */
        System.out.println("Enter the number of elements ");
        n=scr.nextInt();
        d=new int[n];
        /* Accepting elements */
        System.out.println("Enter "+n+" elements: ");
        for(int i=0; i<n; ++i)
            d[i]=scr.nextInt();
        /* Accepting num of clusters */
        System.out.println("Enter the number of clusters: ");
        p=scr.nextInt();
        /* Initialising arrays */
        k=new int[p][n];
        tempk=new int[p][n];
        m=new double[p];
        diff=new double[p];
        /* Initializing m */
        for(int i=0; i<p; ++i)
            m[i]=d[i];
        int temp=0;
        int flag=0;
        do
            {
                for(int i=0; i<p; ++i)
                    for(int j=0; j<n; ++j)
                        {
                            k[i][j]=-1;
                        }
                for(int i=0; i<n; ++i) // for loop will cal cal_diff(int) for every element.
                    {
                        temp=cal_diff(d[i]);
                        if(temp==0)
                            k[temp][count1++]=d[i];
                        else if(temp==1)
                            k[temp][count2++]=d[i];
                        else if(temp==2)
                            k[temp][count3++]=d[i];
                    }
                cal_mean(); // call to method which will calculate mean at this step.
                flag=check1(); // check if terminating condition is satisfied.
                if(flag!=1)
                    /*Take backup of k in tempk so that you can check for equivalence in next step*/
                    for(int i=0; i<p; ++i)
                        for(int j=0; j<n; ++j)
                            tempk[i][j]=k[i][j];
                System.out.println("\n\nAt this step");
                System.out.println("\nValue of clusters");
                for(int i=0; i<p; ++i)
                    {
                        System.out.print("K"+(i+1)+"{ ");
                        for(int j=0; k[i][j]!=-1 && j<n-1; ++j)
                            System.out.print(k[i][j]+" ");
                        System.out.println("}");
                    }//end of for loop
                System.out.println("\nValue of m ");
                for(int i=0; i<p; ++i)
                    System.out.print("m"+(i+1)+"="+m[i]+"  ");
                count1=0;
                count2=0;
                count3=0;
            }
        while(flag==0);
        System.out.println("\n\n\nThe Final Clusters By Kmeans are as follows: ");
        for(int i=0; i<p; ++i)
            {
                System.out.print("K"+(i+1)+"{ ");
                for(int j=0; k[i][j]!=-1 && j<n-1; ++j)
                    System.out.print(k[i][j]+" ");
                System.out.println("}");
            }
    }
}