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Thread: Creating an array that works like a torus

  1. #1
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    Default Creating an array that works like a torus

    I have create a program that takes a random array which is created by starting from 0 and adding Math.random() (double between 0 and 0.999) n times, and calculates the weighted average of each position within a certain radius. I currently have a program that does this but i was wondering how to create one using a torus. The basic principle is the last element is now equal to the first element and when the first element updates its position it takes into account the difference between the other elements including some of the last elements in the array.

    Its not so much help with the coding but with the principle behind it, I cant work out how this would be possible for multiple iterations.

    heres the code so far that works for one iteration. After one the code is incorrect and calculates the wrong values.

    I think using a circular list or a ring buffer may work but i have little experience with either. Any help on the matter would be much appreciated.

     
        import java.text.DecimalFormat;
        import java.util.Scanner;
     
        /**
        * Created by jameshales on 12/03/2014.
         */
        public class Torus {
     
        public static void main(String[] args) {
     
     
            DecimalFormat df = new DecimalFormat("#.###"); 
     
     
            System.out.println("how many numbers of agents on the real line?"); 
     
            Scanner input = new Scanner(System.in);
            int n = 0;
            n=Integer.parseInt(input.nextLine()); 
     
     
            double[] agentPosition = new  double[n];  
            double[] newAgentPosition = new double[n];  
            double[] originalAgentPosition = new double[n];  
     
            System.out.println("Please select your desired radius? select 1 normally"); 
     
     
            double r = 0;
            r = input.nextDouble(); 
     
            int t = 0;  // sets t to 0
     
            double epsilon = 0.001;  
     
            for (int i = 0; i <= n - 1; i++) {  
     
                if (i > 0)
                    agentPosition[i] = agentPosition[i - 1] + Math.random(); // this equation creates the random array 
                else agentPosition[i] =0.0;
            }
     
            System.arraycopy(agentPosition,0,originalAgentPosition,0,n);
     
            while(true) { 
     
                for (int i = 0; i <= n - 1; i++) {
     
                    double total1 = agentPosition[i];    
     
                    double total2 = 0;  
     
                    int numposition = 1; 
     
     
                        for (int j = i - 1; j >= 0; j--) {  
     
                            if ((agentPosition[i] - agentPosition[j]) <= r) {  
     
                                numposition++;        
     
                                total1 += agentPosition[j];  
     
                            } else break;  // stops the program once it has passed a position of a distance of 1
     
                        }
     
                        for (int k = i + 1; k <= n - 1 ; k++) { 
     
                            if (Math.abs(agentPosition[k] - agentPosition[i]) <= r) {     
     
                                numposition++;   
     
                                total2 += agentPosition[k]; 
                            } else break;    
                        }
     
                       for (int j = n - 2; j >= 1; j--) {   
     
                            if (((agentPosition[n-1] + agentPosition[i]) - agentPosition[j]) <= r) {  
     
                                numposition++;
     
                                total1 += (agentPosition[j] - agentPosition[n - 1]);   
     
                            }    else break;
     
                        }
     
                        for (int k = 1; k <= n - 2 ; k++) { 
     
                            if (Math.abs((agentPosition[i] - agentPosition[n - 1]) - agentPosition[k]) <= r) {     /
     
                                numposition++;      
     
                                total2 += (agentPosition[n - 1] + agentPosition[k]); 
     
                            }     else break;
                        }
     
                        newAgentPosition[i] = (total1 + total2) / numposition; // this calculates the new weighted average. ( sum of assigned random variable/ sum of position)
     
                    }
     
                for (int i = 0; i <= n - 1; i++){
     
                    if (newAgentPosition[i] > originalAgentPosition[n - 1]){
                        newAgentPosition[i] = newAgentPosition[i] - originalAgentPosition[n - 1];
                    }
     
                    if(newAgentPosition[i] < 0) {  
                        newAgentPosition[i] = newAgentPosition[i] + originalAgentPosition[n - 1];
                    }
     
                }
     
                t++;  // This sums up how many iterations it will take.
     
                double largestDiff = 0.0;  // This assigns largestDiff to 0
     
                for (int i = 0; i <= n-1; i++) {
     
                    double diff = Math.abs(agentPosition[i] - newAgentPosition[i]);  // This calculates the difference between the previous and current array at position i.
     
                    if(diff > largestDiff)  // If the difference between the agents is bigger than 0, assign it to the variable largestDiff.
                        largestDiff = diff;
     
                }
     
                if(largestDiff <= epsilon){  // This checks if the difference is bigger than the set epsilon,
     
                    break;  // This stops the program if the difference is smaller than epsilon
                }
     
                agentPosition = new double[n];
     
                System.arraycopy(newAgentPosition, 0, agentPosition, 0, n);  
     
            }
     
            for (int i = 0 ; i <= n - 1; i++) {   
     
                System.out.println(i + ": " + df.format(originalAgentPosition[i]) + "\t->\t" + df.format(agentPosition[i]));
     
            }
     
            int sumdofclusters = 1;  // This sets the sum of clusters to 1
     
            System.out.println("The different clusters are:\n" + df.format(agentPosition[0]));   // This prints out the first cluster only.
     
            for (int i = 1; i <= n - 1 ; i++) {
     
                if(Math.abs(agentPosition[i] - agentPosition[i - 1]) >= epsilon) {  // This checks if the element after the element at hand is different by a set epsilon.(how to work out different clusters)
     
                    sumdofclusters++;  // This sums the number of clusters.
     
     
                    System.out.println(df.format(agentPosition[i])); // This prints out the different clusters other than the first 1.
                }
     
            }
            System.out.println("Number of clusters is:" + sumdofclusters); // This prints out the number of clusters.
     
            System.out.println("Number of iterations:" + t);   // This prints out the number of iterations.
     
     
        }
        }
    Last edited by jameshales; March 15th, 2014 at 07:06 AM.


  2. #2
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    Default Re: Creating an array that works like a torus

    Welcome to the forum! Please read this topic to learn how to post code correctly and other useful info for new members.

    Please edit your post so that the code is posted correctly and code formatting is preserved.

    Sample runs would be helpful. Show what the program's output looks like when "it works" and when it doesn't and explain the difference. Since we're not all math majors, some may have trouble following you. Well, I do.

  3. #3
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    Default Re: Creating an array that works like a torus

    Also posted at: Creating an array that works like a torus
    If you don't understand my answer, don't ignore it, ask a question.

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