//NormalPoints.java
//2D Gaussian distribution normal distribution around center of applet area as mean

import java.awt.*;
import javax.swing.*;

public class NormalPoints extends JApplet {     

    int points, circles;
    double variance;
    String pointsOrCircles;
    
    public void init() {
	String input;

	pointsOrCircles = JOptionPane.showInputDialog( "Points (p) or circles (c)?");
 
	if (pointsOrCircles.equalsIgnoreCase("p")) {
 	    input = JOptionPane.showInputDialog( "Enter number of points" );
	    points = Integer.parseInt(input);
	}
	else {
 	    input = JOptionPane.showInputDialog( "Enter number of circles" );
	    circles = Integer.parseInt(input);
	
	}
	
	input = JOptionPane.showInputDialog( "Enter standard deviation" );
	variance = Double.parseDouble(input);
	
    }
    
    
    public void paint (Graphics g) {
	int x, y=0, length;
	double angle;
	int midw=getWidth()/2;   //mean X
	int midh=getHeight()/2;  //mean Y
        int sd1=0, sd2=0, sd3=0;
		
	if (pointsOrCircles.equalsIgnoreCase("p")) {
	    for (int i=1; i<=points; i++) {
	        //x = (int)(midw + ((2*(Math.random()+Math.random()+Math.random())-3) * variance));
	        length = Math.abs((int)((2*(Math.random()+Math.random()+Math.random())-3) * variance));
	        angle = Math.random() * 2 * Math.PI;    //radians
	        x = (int)(Math.cos(angle) * length + midw);
	        y = (int)(Math.sin(angle) * length + midh);	
	        if (length<=variance) {
	            sd1++;
	            //y = midh + (int)((2*Math.random()-1) * variance);
	        } 
	        else if (length<=2*variance) {
	            sd2++;
	            //y = midh + (int)((4*Math.random()-2) * 2*variance);
	        } 
	        else if (length<=3*variance) {
	            sd3++;
	            //y = midh + (int)((6*Math.random()-4) * 3*variance);
	        }
	        //y = (int)(midh + ((2*(Math.random()+Math.random()+Math.random())-3) * variance));
	        g.drawLine(x,y, x,y);
	    }
	    g.setColor(Color.RED);
	    int iSD = (int)variance;
	    g.drawOval(midw-iSD,midh-iSD,2*iSD,2*iSD);
	    g.drawOval(midw-iSD*2,midh-iSD*2,4*iSD,4*iSD);
	    g.drawOval(midw-3*iSD,midh-3*iSD,6*iSD,6*iSD);
	    showStatus("#<1S: "+sd1+"  #<2S: "+(sd1+sd2)+"  #<3S: "+(sd1+sd2+sd3));
	}
	else {
	    int[] A = new int[circles];
	    int sumX=0;
	    for (int i=1; i<=circles; i++) {
	        x = 2*Math.abs((int)(((2*(Math.random()+Math.random()+Math.random())-3) * variance)));
	        A[i-1] = x;
	        sumX += x;
	        //y = (int)(midh + ((2*(Math.random()+Math.random()+Math.random())-3) * variance));
	        g.drawOval(midw-x/2,midh-x/2,x,x);
	    }
	    double sampleMean = (double)sumX/circles;
	    double sumSqrdDiffs=0;
	    for (int i=0; i<circles; i++)
	        sumSqrdDiffs += (A[i]-sampleMean)*(A[i]-sampleMean);
	    double sampleSD = Math.sqrt(sumSqrdDiffs/(circles-1));	    
	    for (int i=0; i<circles; i++)
	    	if (A[i] <= 2*variance)
	    	    sd1++;
	    	else if (A[i] <= 4*variance)
	    	    sd2++;
	    	else if (A[i] <= 6*variance)
	    	    sd3++;
	    	    
	    showStatus("s= "+((int)sampleSD)+
	    	"  #<1S: "+sd1+"  #<2S: "+(sd1+sd2)+"  #<3S: "+(sd1+sd2+sd3));
	    g.setColor(Color.RED);
	    int iSD = (int)sampleSD;
	    g.drawOval(midw-iSD,  midh-iSD,   2*iSD,2*iSD);
	    g.drawOval(midw-2*iSD,midh-2*iSD, 4*iSD,4*iSD);
	    g.drawOval(midw-3*iSD,midh-3*iSD, 6*iSD,6*iSD);
	}
    }
}