// BinomialPlot.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 BinomialPlot
	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, numl3, numl4;			// Controls
	TextField num1, num2, num3, num4;
	Button go;
	
	GridBagLayout gbl;
	GridBagConstraints cc;
		
	// Initialize applet
	public void init()
	{	
		numl1 = new Label("  n1 = ");			// Create controls
		num1 = new TextField("40", 4);
		numl2 = new Label("  n2 = ");			// Create controls
		num2 = new TextField("80", 4);
		numl3 = new Label("  n3 = ");			// Create controls
		num3 = new TextField("160", 4);
		numl4 = new Label("  p = ");			// Create controls
		num4 = new TextField(".5", 4);
		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(num1, cc);
		controls.add(num1);
		
		cc.gridx = 2;
		gbl.setConstraints(numl2, cc);
		controls.add(numl2);
		
		cc.gridx = 3;
		gbl.setConstraints(num2, cc);
		controls.add(num2);
		
		cc.gridx = 4;
		gbl.setConstraints(numl3, cc);
		controls.add(numl3);
		
		cc.gridx = 5;
		gbl.setConstraints(num3, cc);
		controls.add(num3);
		
		cc.gridx = 0;
		cc.gridy = 1;
		gbl.setConstraints(numl4, cc);
		controls.add(numl4);
		
		cc.gridx = 1;
		gbl.setConstraints(num4, cc);
		controls.add(num4);
		
		cc.gridx = 2;
		cc.gridwidth = 4;
		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(num1.getText()).intValue(),
        			Integer.valueOf(num2.getText()).intValue(),
        			Integer.valueOf(num3.getText()).intValue(),
        			Float.valueOf(num4.getText()).floatValue());
        		return true;					// Generate correct number of tosses
			}
		}
		return super.handleEvent(evt);	// Handle other events as usual
	}
	
	// Calculate probabilities
    public void simulate(int num1, int num2, int num3, float prob)
    {	
    	float temp;
    	int length = (int) Math.max(Math.max((double) num1, (double) num2), 
    		(double) num3) + 1;
    	xCoords = new Float[length];
    	yCoords = new Float[length];
    	for (int i = 0; i < length; i++) {
    		xCoords[i] = new Float(i);
    		temp = Combinatorics.bernoulli(num1, prob, i) +
    			Combinatorics.bernoulli(num2, prob, i) +
    			Combinatorics.bernoulli(num3, prob, i);
    		yCoords[i] = new Float(temp);
	    }
		dispArea.remove(sg);
		sg = new SpikeGraph(xCoords, yCoords);	// Create new SpikeGraph
		dispArea.add(sg);							// Put up the graph
		validate();
	}
}