//BinomialCurve.java

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;
import java.util.*;
import java.text.*;

public class BinomialCurve extends JApplet implements ActionListener {     

    double p, yScale=1;
    int n, numBinomials, binNums[], cdfK;
    JPanel controlPanel;
    JLabel nLabel, pLabel, yScaleLabel, numBinomialsLabel, cdfLabel;  
    JTextField nTextField, pTextField, yScaleTextField, numBinomialsTextField, cdfTextField; 
    JButton yScaleUpButton, yScaleDownButton, showBinomialsButton;
    JTextArea binomialtextarea;
    JScrollPane binomialscrollpane;
    JSlider cdfSlider;
    DecimalFormat d4;
    
    public void init() {
	String input;

	Container container = getContentPane();
	container.setLayout( new BorderLayout() ); 

	controlPanel = new JPanel();
	controlPanel.setLayout(new FlowLayout());
	controlPanel.setBackground(Color.MAGENTA);
	controlPanel.setBorder(BorderFactory.createEtchedBorder(EtchedBorder.RAISED));
	container.add(controlPanel,BorderLayout.NORTH);

	nLabel = new JLabel( "n" );
	controlPanel.add( nLabel );
	nTextField = new JTextField("10",3);
	n = Integer.parseInt(nTextField.getText());
	nTextField.setHorizontalAlignment(JTextField.RIGHT);
	nTextField.addActionListener( this );
	controlPanel.add( nTextField );

	pLabel = new JLabel( "p" );
	controlPanel.add( pLabel );
	pTextField = new JTextField("0.5",4);
	p = Double.parseDouble(pTextField.getText());
	pTextField.setHorizontalAlignment(JTextField.RIGHT);
	pTextField.addActionListener( this );
	controlPanel.add( pTextField );
	
	cdfLabel = new JLabel( "CDF" );
	controlPanel.add( cdfLabel );
	cdfTextField = new JTextField("0",4);
	cdfTextField.setBackground(Color.GREEN);
	cdfTextField.setForeground(Color.BLACK);
	cdfTextField.setHorizontalAlignment(JTextField.RIGHT);
	cdfTextField.setEditable(false);
	cdfTextField.addActionListener( this );
	controlPanel.add( cdfTextField );
	
	//how to redraw when n changes
	cdfSlider = new JSlider( SwingConstants.HORIZONTAL, 0, n, 0 );
	cdfSlider.setMajorTickSpacing(1);
	cdfSlider.setPaintTicks(true);
	cdfSlider.setPaintLabels(true);
	cdfSlider.setSnapToTicks(true);
	cdfSlider.addChangeListener(
	        new ChangeListener() {  // anonymous inner class
		    // handle change in slider value
		    public void stateChanged( ChangeEvent e ) {
			cdfK = cdfSlider.getValue();
			System.out.println("cdfK="+cdfK);
			repaint();
		    }
		}
	);
	controlPanel.add(cdfSlider);
			
	yScaleLabel = new JLabel( "y scale" );
	controlPanel.add( yScaleLabel );
	yScaleTextField = new JTextField("1",4);
	yScale = Double.parseDouble(yScaleTextField.getText());
	yScaleTextField.setHorizontalAlignment(JTextField.RIGHT);
	yScaleTextField.addActionListener( this );
	controlPanel.add( yScaleTextField );
	
	yScaleUpButton = new JButton( "+" );
	controlPanel.add( yScaleUpButton );
	yScaleUpButton.addActionListener( this );

	yScaleDownButton = new JButton( "-" );
	controlPanel.add( yScaleDownButton );
	yScaleDownButton.addActionListener( this );

	numBinomialsLabel = new JLabel( "Sample size" );
	controlPanel.add( numBinomialsLabel );
	numBinomialsTextField = new JTextField("100",4);
	numBinomials = Integer.parseInt(numBinomialsTextField.getText());
	numBinomialsTextField.setBackground(Color.BLUE);
	numBinomialsTextField.setForeground(Color.WHITE);
	numBinomialsTextField.setHorizontalAlignment(JTextField.RIGHT);
	numBinomialsTextField.addActionListener( this );
	controlPanel.add( numBinomialsTextField );
	
	showBinomialsButton = new JButton( "Show sample" );
	controlPanel.add( showBinomialsButton );
	showBinomialsButton.addActionListener( this );

	d4 = new DecimalFormat (".0000");
	
 	binomialtextarea = new JTextArea(20,100); 
 	binomialtextarea.setLineWrap( true );
 	binomialtextarea.setFont( new Font("Courier",Font.BOLD,14) );
	binomialscrollpane = new JScrollPane(binomialtextarea);
		
//	zTextField.setText("1.0");  //fires listener? no
//	zTextField.postActionEvent();

   }

    public void actionPerformed( ActionEvent event ) {
    	try {
    	    int nTry = Integer.parseInt(nTextField.getText());
    	    double pTry = Double.parseDouble(pTextField.getText());
    	    numBinomials = Integer.parseInt(numBinomialsTextField.getText());
	    double yScaleTry = Double.parseDouble(yScaleTextField.getText());
	}
	catch (NumberFormatException e) {
	    JOptionPane.showMessageDialog(null,
					  " must be a number",
					  "BinomialCurve: Invalid input",
					  JOptionPane.ERROR_MESSAGE);
	    return;
	}
    	if ( event.getSource() == nTextField ) {
    	    int oldN = n;
	    n = Integer.parseInt(nTextField.getText());
	    if (n != oldN ) {
	        cdfSlider.setMaximum(n);   //set the new max
	        cdfSlider.setValue(0);  //reset to 0
	        cdfK = 0;
	    }
	    repaint();    
	}
    	else if ( event.getSource() == numBinomialsTextField ) {
	    numBinomials = Integer.parseInt(numBinomialsTextField.getText());
	    repaint();    
	}
	else if ( event.getSource() == pTextField ) {
	    double oldp = p;
	    p = Double.parseDouble(pTextField.getText());
	    if (p<0 || p>1.0) {
	    	JOptionPane.showMessageDialog(null,
					  "0 <= p <= 1.0",
					  "BinomialCurve: Invalid input",
					  JOptionPane.ERROR_MESSAGE);
		p = oldp;	    
		pTextField.setText(""+d4.format(p));
	    }
	    else
	    	repaint();    
	}
 	else if ( event.getSource() == yScaleTextField ) {
 	    double oldYscale = yScale;
	    yScale = Double.parseDouble(yScaleTextField.getText());
	    if (yScale < 0) {
	    	JOptionPane.showMessageDialog(null,
					  "y scale can not be negative",
					  "NormalCurve: Invalid input",
					  JOptionPane.ERROR_MESSAGE);
		yScale = oldYscale;
		yScaleTextField.setText(""+yScale);
	    }
	    else
	        repaint();    
	}   
	else if ( event.getSource() == yScaleUpButton ) {
	    yScale++;
	    yScaleTextField.setText(""+yScale);
	    repaint();    
	}
	else if ( event.getSource() == yScaleDownButton ) {
	    if (yScale > 1) {
	        yScale--;
	        yScaleTextField.setText(""+yScale);
	        repaint();    
	    }
	}
	else if ( event.getSource() == showBinomialsButton ) {
	    int k, sum=0, sumSqrd=0;
            double mean, sd;
	    for (int i=0; i<numBinomials; i++) {
	    	sum += binNums[i];
	    	sumSqrd += binNums[i]*binNums[i];
	    	binomialtextarea.append(" "+binNums[i]);
	    }
            mean = (double)sum/numBinomials;
            binomialtextarea.append("\n\nmean="+d4.format(mean));
            sd = Math.sqrt((sumSqrd - numBinomials*(mean*mean)) / (numBinomials-1) );
            binomialtextarea.append("  sd="+d4.format(sd));
	    
	    JOptionPane.showMessageDialog(null, binomialscrollpane,
                             ""+numBinomials+" Binomial-distributed random numbers: n="+n+" p="+p,
			      JOptionPane.PLAIN_MESSAGE);
	    binomialtextarea.setText("");
	}
	
    }
    
    public void paint (Graphics g) {
	super.paint( g );   //erase 
	int w = getWidth();
	int h = getHeight();
	int bottomOffset=10, yi, xi;
	g.setFont(new Font("Courier",Font.BOLD,14));
	//y axis
	g.drawLine(0,50, 0,h-bottomOffset);
	// x axis
	g.drawLine(0,h-bottomOffset,w,h-bottomOffset);

	System.out.println("");
	g.setColor(Color.BLACK);
	g.drawString("Prob.", 5,80); 
	g.drawString("k", w-10,h); 
	g.setColor(Color.RED);
	g.drawString("Theoretical",50,70);
       	g.setColor(Color.BLUE);
       	g.drawString("Sample", w-200,70);

	double y, cdf=0;
	double nChooseK;   //nC0 =1
	
	for (int k=0; k<=n; k++) {    //each "k successes" value
	    nChooseK = 1;
	    for (int i=1; i<=k; i++)      //dumb
	    	nChooseK *= (double)(n-(k-i))/i;
	    	
	    y = nChooseK * Math.pow(p,k) * Math.pow(1-p,n-k);
	    //nChooseK *= 
	    	
	    //System.out.println("k="+k+" y="+  y+"  nCk="+nChooseK);
	    yi = h - (int)(y*yScale*h) - bottomOffset;
	    xi = (int)((double)k/(n+1) * w);
	    if (k <= cdfK) {
		cdf += y;
	        g.setColor(Color.GREEN);
	    }
	    else
	    	g.setColor(Color.RED);
	    g.fillRect(xi,yi,4,h-yi-bottomOffset);
	    g.setColor(Color.RED);
	    g.drawString(""+d4.format(y),xi+2,yi-1);
	    
	    g.setColor(Color.BLACK);
	    g.drawLine(xi,h-bottomOffset,xi,h-bottomOffset-4);   //k tick
	    g.drawString(""+k, xi,h);   //k value on x axis
	    if (k == Math.round(n*p)) {  //a max y?   ==mean
	        g.setColor(Color.RED);
	        g.drawLine(1,yi,  5,yi);
	        g.drawString(""+d4.format(y), 6,yi); 
	    }
	}

	cdfTextField.setText(""+d4.format(cdf));

        //generate binomial-distributed numbers.  a sample
        binNums = new int[numBinomials];
        int binNumsFreq[] = new int[n+1];
	int kGen;
	for (int i=0; i<numBinomials; i++) {
	    kGen = 0;
	    for (int j=1; j<=n; j++)
	        if (Math.random() < p)
	       	    kGen++;
	    binNums[i] = kGen;
	    binNumsFreq[kGen]++;
	}		

       	g.setColor(Color.BLUE);
       	for (int k=0; k<=n; k++) {
       	    yi = h - (int)((double)binNumsFreq[k]/numBinomials*yScale*h) - bottomOffset;
	    xi = (int)((double)k/(n+1) * w);
	    //System.out.print("\nxi="+xi+"  yi="+yi);
	    g.fillRect(xi,yi-2,4,4);
       	}		

    }
}