// NFoldConvolution.java

// Written by Julian Devlin, 8/97, for the text book
// "Introduction to Probability," by Charles M. Grinstead & J. Laurie Snell

import java.applet.Applet;
import java.awt.*;

public class NFoldConvolution
	extends java.applet.Applet
{
	Float[] xCoords;		// Variables for simulation
	Float[] yCoords;
	
	SpikeGraph sg;				// AWT elements
	
	Panel dispArea;
	Panel controls;		// Panel for user controls
	
	Label numl1, numl2;			// Controls
	TextField num;
	Button go;
	
	GridBagLayout gbl;
	GridBagConstraints cc;
	
	float[] probs = {36f/52f, 4f/52f, 4f/52f, 4f/52f, 4f/52f};
		
	// Initialize applet
	public void init()
	{	
		numl1 = new Label("P(C >=");			// Create controls
		num = new TextField("13", 4);
		numl2 = new Label(") =                    ");
		go = new Button("Go");
		
		sg = new SpikeGraph(); // initialize a graphing space
		
		dispArea = new Panel();				// Set up window
		controls = new Panel();
		setLayout(new BorderLayout(5, 5));
		
		add("South", controls);
		add("Center", dispArea);
		
		dispArea.setLayout(new GridLayout(1, 1));
		dispArea.add(sg);
		
		gbl = new GridBagLayout();
		controls.setLayout(gbl);
		
		cc = new GridBagConstraints();
		
		cc.gridx = 0;
		cc.gridy = 0;
		gbl.setConstraints(numl1, cc);
		controls.add(numl1);
		
		cc.gridx = 1;
		gbl.setConstraints(num, cc);
		controls.add(num);
		
		cc.gridx = 2;
		gbl.setConstraints(numl2, cc);
		controls.add(numl2);
		
		cc.gridx = 0;
		cc.gridy = 1;
		cc.gridwidth = 3;
		gbl.setConstraints(go, cc);
		controls.add(go);
		
		validate();
	}
	
	// Handle events
	public boolean handleEvent(Event evt)
	{
		if (evt.target instanceof Button)
		{
			if (evt.target == go && evt.id == Event.ACTION_EVENT)	// When button is clicked
			{
        		simulate(Integer.valueOf(num.getText()).intValue());
        		return true;					// Generate correct number of tosses
			}
		}
		return super.handleEvent(evt);	// Handle other events as usual
	}
	
	public float[] convolve(float[] d1, float[] d2) {
		float[] results = new float[d1.length + d2.length - 1];
		for (int i = 0; i < results.length; i++) {
			results[i] = 0;	
		}
		for (int i = 0; i < d1.length; i++) {
			for (int j = 0; j < d2.length; j++) {
				results[i + j] += d1[i] * d2[j];	
			}	
		}	
		return results;
	}
	
	// Calculate probabilities
    public void simulate(int score)
    {	
    	xCoords = new Float[31];
    	yCoords = new Float[31];
    	float[] temp;
    	float openings = 0;
    	
    	for (int i = 0; i < xCoords.length; i++) {
    		xCoords[i] = new Float(i);
       	}
    	
    	temp = probs;
    	for (int i = 1; i < 13; i++) {
    		temp = convolve(temp, probs);
    	}
    		
    	
    	for (int i = 0; i < yCoords.length; i++) {
    		yCoords[i] = new Float(temp[i]);
    		if (i >= score)
    			openings += temp[i];
    	}
    	
		dispArea.remove(sg);
		sg = new SpikeGraph(xCoords, yCoords);	// Create new SpikeGraph
		dispArea.add(sg);							// Put up the graph
		numl2.setText(") = " + String.valueOf(openings));
		validate();
	}
}