// <APPLET CODE="Plot.class" WIDTH=465 HEIGHT=412></APPLET>

import java.awt.*;
import java.applet.*;
import java.math.*;

public class Plot extends Applet {
	final Color myColor = new Color(255,200,200);
	static TextField2 tf_A11, 
				tf_A12, 
				tf_A21, 
				tf_A22,
		    		tf_x1,  
				tf_x2,
		    		tf_b1,  
				tf_b2,
				tfcondition ;
	static Choice c7;
	GraphPanel gp;

	public void init(){
		setLayout(new BorderLayout());
		createTextField2s();

		Panel pete = new Panel();
		//pete.setLayout(new GridLayout(1,2));
		pete.setLayout(new BorderLayout());

		gp = new GraphPanel(300,300);
		gp.setBackground(myColor);
		gp.setEquation(2.0,3.0,8.0,5.0,4.0,13.0);		
		pete.add("Center",gp);

		Panel pp1 = new Panel();
		pp1.setLayout(new GridLayout(7,1));
		pp1.setBackground(myColor);

		Panel pp = new Panel();
		pp.setBackground(myColor);
		tfcondition =  new TextField2(8,this);
		pp.add(new Label("Condition:"));
		pp.add(tfcondition);

		pp1.add(new Button("Zoom In"));
		pp1.add(new Button("Zoom Out"));
		pp1.add(new Button("Example #1"));
		pp1.add(new Button("Choose Random"));
		pp1.add(new Button("Calculate"));

		Panel p_Choice = new Panel();
		Choice c = new Choice();
		for (int i=1;i<=10;i++)
			c.addItem(""+i);
		c.select(2);
		p_Choice.add(new Label("Precision: "));
		p_Choice.add(c);

		pp1.add(p_Choice);
		c7 = c;

		pp1.add(pp);
		pete.add("East",pp1);

		add("South",embedPanels());
		add("Center",pete);
	}

	public Panel embedPanels(){
		Panel pete = new Panel();
		pete.setLayout(new BorderLayout());
		pete.setBackground(myColor);

		pete.add("Center",createPanels());
		pete.add("North",createButtons());
		return pete;
	}

	public void createTextField2s(){
		tf_A11 = new TextField2(8,this);
		tf_A12 = new TextField2(8,this);
		tf_A21 = new TextField2(8,this);
		tf_A22 = new TextField2(8,this);
		tf_x1 = new TextField2(8,this);
		tf_x2 = new TextField2(8,this);
		tf_b1 = new TextField2(8,this);
		tf_b2 = new TextField2(8,this);
		tf_A11.setText(""+2);
		tf_A12.setText(""+3);
		tf_A21.setText(""+5);
		tf_A22.setText(""+4);
		tf_b1.setText(""+8);
		tf_b2.setText(""+13);
	}

	public Panel createButtons(){
		Panel p_But = new Panel();
		p_But.add(new Button("Example #1"));
		p_But.add(new Button("Choose Random"));
		p_But.add(new Button("Calculate"));

		Panel p_Choice = new Panel();
		Choice c = new Choice();
		for (int i=1;i<=10;i++)
			c.addItem(""+i);
		c.select(2);
		p_Choice.add(new Label("Precision: "));
		p_Choice.add(c);

		p_But.add(p_Choice);
		return new Panel();
	}

	public Panel createPanels(){
		Panel p1 = new Panel();
		p1.setLayout(new GridLayout(4,1));
		p1.add(new Label("a11"));
		p1.add(tf_A11);
		p1.add(new Label("a21"));
		p1.add(tf_A21);

		Panel p2 = new Panel();
		p2.setLayout(new GridLayout(4,1));
		p2.add(new Label("a12"));
		p2.add(tf_A12);
		p2.add(new Label("a22"));
		p2.add(tf_A22);

		Panel p3 = new Panel();
		p3.setLayout(new GridLayout(4,1));
		p3.add(new Label("x1"));
		p3.add(tf_x1);
		p3.add(new Label("x2"));
		p3.add(tf_x2);

		Panel p4 = new Panel();
		p4.setLayout(new GridLayout(4,1));
		p4.add(new Label("b1"));
		p4.add(tf_b1);
		p4.add(new Label("b2"));
		p4.add(tf_b2);
		
		Panel p_Equal = new Panel();
		p_Equal.setLayout(new GridLayout(4,1));
		p_Equal.add(new Label(" "));
		p_Equal.add(new Label("="));
		p_Equal.add(new Label(" "));
		p_Equal.add(new Label("="));

		Panel p_Control = new Panel();
		p_Control.setBackground(myColor);
		p_Control.add(p1);
		p_Control.add(p2);
		p_Control.add(p3);
		p_Control.add(p_Equal);
		p_Control.add(p4);

		return p_Control;
	}

public boolean action(Event evt, Object arg){
	if (arg.equals("Zoom In")){
		gp.factor=gp.factor*1.5;

		gp.shiftx = (int)Math.round(gp.z1*gp.factor);
		gp.shifty = (int)Math.round(gp.z2*gp.factor);

		gp.repaint();
		repaint();
	}

 	if (arg.equals("Zoom Out")){
		gp.factor=gp.factor*2.0/3.0;

		gp.shiftx = (int)Math.round(gp.z1*gp.factor);
		gp.shifty = (int)Math.round(gp.z2*gp.factor);

		gp.repaint();
		repaint();
	}

	if (evt.target instanceof Choice){
		fixPrecision();
		//GraphPanel.showMe = true;  // was2
		doPiv();
		fixPrecision();
		gp.setEquation(Double.valueOf(tf_A11.getText()).doubleValue(),
			Double.valueOf(tf_A12.getText()).doubleValue(),
			Double.valueOf(tf_b1.getText()).doubleValue(),
			Double.valueOf(tf_A21.getText()).doubleValue(),
			Double.valueOf(tf_A22.getText()).doubleValue(),
			Double.valueOf(tf_b2.getText()).doubleValue());
		fixPrecision();
	}

	if (arg.equals("Calculate") || arg.equals("Choose Random")){
		if (arg.equals("Choose Random"))
			generateRandom();
		fixPrecision();
		GraphPanel.showMe = true;  //was2
		doPiv();
		fixPrecision();
		gp.setEquation(Double.valueOf(tf_A11.getText()).doubleValue(),
			Double.valueOf(tf_A12.getText()).doubleValue(),
			Double.valueOf(tf_b1.getText()).doubleValue(),
			Double.valueOf(tf_A21.getText()).doubleValue(),
			Double.valueOf(tf_A22.getText()).doubleValue(),
			Double.valueOf(tf_b2.getText()).doubleValue());
		fixPrecision();
		gp.shiftx=0;
		gp.shifty=0;
	}


	if (arg.equals("Example #1")){
		tf_A11.setText("2");
		tf_A12.setText("3");
		tf_A21.setText("5");
		tf_A22.setText("4");
		tf_b1.setText("8");
		tf_b2.setText("13");
		fixPrecision();
		double a[][] = new double[4][4];
		a[1][1]= Double.valueOf(tf_A11.getText()).doubleValue();
		a[1][2]=Double.valueOf(tf_A12.getText()).doubleValue();
		a[1][3]=Double.valueOf(tf_b1.getText()).doubleValue();
		a[2][1]=Double.valueOf(tf_A21.getText()).doubleValue();
		a[2][2]=Double.valueOf(tf_A22.getText()).doubleValue();
		a[2][3]=Double.valueOf(tf_b2.getText()).doubleValue();
		//GraphPanel.showMe = true; //was2
		doPiv();
		fixPrecision();

		gp.setEquation(Double.valueOf(tf_A11.getText()).doubleValue(),
			Double.valueOf(tf_A12.getText()).doubleValue(),
			Double.valueOf(tf_b1.getText()).doubleValue(),
			Double.valueOf(tf_A21.getText()).doubleValue(),
			Double.valueOf(tf_A22.getText()).doubleValue(),
			Double.valueOf(tf_b2.getText()).doubleValue());	
		gp.shiftx=0;
		gp.shifty=0;
	}
	return true;
}

	public void generateRandom(){
		double multiple = c7.getSelectedIndex()+1;
		multiple = Math.pow(10,multiple);
		tf_A11.setText(""+Math.round(1+((Math.random()-.5)*multiple)));
		tf_A12.setText(""+Math.round(1+((Math.random()-.5)*multiple)));
		tf_A21.setText(""+Math.round(1+((Math.random()-.5)*multiple)));
		tf_A22.setText(""+Math.round(1+((Math.random()-.5)*multiple)));
	
		tf_b1.setText(""+Math.round(1+((Math.random()-.5)*multiple)));
		tf_b2.setText(""+Math.round(1+((Math.random()-.5)*multiple)));
		tf_x1.setText("");
		tf_x2.setText("");
	}

//////////////////////////// Partial Pivoting ////////////////////////////////
public void doPiv(){
		double a[][] = new double[4][4];
		a[1][1]= Double.valueOf(tf_A11.getText()).doubleValue();
		a[1][2]=Double.valueOf(tf_A12.getText()).doubleValue();
		a[1][3]=Double.valueOf(tf_b1.getText()).doubleValue();
		a[2][1]=Double.valueOf(tf_A21.getText()).doubleValue();
		a[2][2]=Double.valueOf(tf_A22.getText()).doubleValue();
		a[2][3]=Double.valueOf(tf_b2.getText()).doubleValue();
	//	System.out.println("Condition:"+condition(a[1][1],a[1][2],a[2][1],a[2][2]));
		tfcondition.setText(GraphPanel.correctScale(
			new BigDecimal(""+condition(a[1][1],a[1][2],a[2][1],a[2][2])),
			c7.getSelectedIndex()+1).toString());
		doPiv_(2,a);
}

public void fixPrecision(){
		tf_A11.setText(GraphPanel.correctScale(new BigDecimal(tf_A11.getText()),c7.getSelectedIndex()+1).toString());
		tf_A12.setText(GraphPanel.correctScale(new BigDecimal(tf_A12.getText()),c7.getSelectedIndex()+1).toString());
		tf_A21.setText(GraphPanel.correctScale(new BigDecimal(tf_A21.getText()),c7.getSelectedIndex()+1).toString());
		tf_A22.setText(GraphPanel.correctScale(new BigDecimal(tf_A22.getText()),c7.getSelectedIndex()+1).toString());
		tf_b1.setText(GraphPanel.correctScale(new BigDecimal(tf_b1.getText()),c7.getSelectedIndex()+1).toString());
		tf_b2.setText(GraphPanel.correctScale(new BigDecimal(tf_b2.getText()),c7.getSelectedIndex()+1).toString());

	try {
		if (!tf_x1.getText().equals(""))
		tf_x1.setText(GraphPanel.correctScale(new BigDecimal(tf_x1.getText()),c7.getSelectedIndex()+1).toString());

		if (!tf_x2.getText().equals(""))
		tf_x2.setText(GraphPanel.correctScale(new BigDecimal(tf_x2.getText()),c7.getSelectedIndex()+1).toString());
	} catch (NumberFormatException e){}

}

public void doPiv_(int n, double a[][]) {
	int count=0;
	//next loop and the following 2 statements put the matrix system in
	//diagonal form with 1's on the diagonal
	for (int i=1;i<=n-1;i++) {
	   	double m = Math.abs(a[i][i]);
	   	int c = i;
	   	// next loop finds the highest element down the column
	   	for (int j=i+1;j<=n;j++) 
			if (Math.abs(a[j][i])> m) {
	      	   	m = Math.abs(a[j][i]);
	         		c = j;
			}

	   	//next loop interchanges rows i and c
	   	for (int j=i;j<=n+1;j++) {
	      	double d = a[i][j];
			a[i][j] = a[c][j];	
			a[c][j] = d;
			count++;
	   	} // end for j

   	//next loop divids row i by a(i,i)
   	for (int j=n+1;j >= i; j--) 
		a[i][j] = a[i][j] / a[i][i];
   	//next loop subracts appropriate multiples of row i from rows below
   	for (int j=i+1;j<=n;j++) 
		for (int k=n+1; k >= i; k--) 
		   	a[j][k] = a[j][k] - a[j][i] * a[i][k];
	} //end for i

	//next two statements fix the last row
	a[n][n+1] = a[n][n+1]/a[n][n];
	a[n][n]=1;
	//next loop transforms the triangular matrix to the identity matrix
	//plus a column (the last column) which is the solution vector
	for (int i=n;i>=2; i--) 
	   	for (int k=i-1;k>=1;k--)
			for (int j=n+1;j>=i;j--) {
				//System.out.println("value8 "+a[k][j]+" N: "+n);
	   			a[k][j] = a[k][j] - a[k][i]*a[i][j];
				//System.out.println("value9 "+a[k][j]);
			}

	//next loop prints the solution
	//for (int i=1;i<=n;i++) 
   		//System.out.println("x"+i+" is equal to "+a[i][n+1]);
	tf_x1.setText(""+a[1][2+1]);
	tf_x2.setText(""+a[2][2+1]);
	gp.z1 = a[1][3];
	gp.z2 = a[2][3];
}

//////////////////////////// End Partial Pivoting /////////////////////////////
public double condition (double a11,double a12, double a21, double a22){
	double p = a11*a11+a21*a21;
	double q = a11*a12+a21*a22;
	double r = a12*a12+a22*a22;
	double t = p+r;
	double d = t*t-4.0*(p*r-q*q);
	double s = Math.sqrt(d);
	double x = t+s;
	double y = t-s;
	if (y <= 0){
		System.out.println("Condition number is infinite & matrix is singular.");
		return 0;
	}
	double z = x/y;
	//System.out.println("z: "+z);
	return Math.sqrt(z);
}
////////////////////////////////////////////////////////////////////////////////
} // End class
//
////////////////////////////////////////////////////////////////
//
class GraphPanel extends Panel {
	int w, 
	    h,shiftx=0,shifty=0;
	double x,
		 y,
		 b,
		 factor,
		 z1,
		 z2;
	static double factor2=1.0;
	double x_, y_, b_;
	static boolean showMe;

	public GraphPanel(int w, int h){
		this.w = w;
		this.h = h;
		shiftx=0;
		shifty=0;
	}

	public void paint(Graphics g){
		g.setColor(Color.white);
		g.fillRect(0,0,w,h);
		drawAxis(g);
		g.setColor(Color.red);
		drawEquationFuzz(g);
		drawEquation(g);

		// Clear Edges
		g.setColor(new Color(255,200,200));	
		g.fillRect(0,h,w,h+200);
		g.fillRect(w,h,w,h+200);

		// Draw Box around graph
		g.setColor(Color.black);
		g.drawRect(0,0,w-1,h-1);
	}

	public void drawAxis(Graphics g){
		g.setColor(Color.blue);
		// Vertical Line
		g.drawLine(scaleX((reScaleX(h/2))),0,scaleX((reScaleX(h/2))),h);

		// Horizontal Line
		g.drawLine(0,scaleY((reScaleY(w/2))),h,scaleY((reScaleY(w/2))));

	// Draw graph ticks
	//----------------------------------------------------------------------------
	// Hash marks on horizontal line
	g.drawLine(-shiftx+3,scaleY(reScaleY(h/2-2)),-shiftx+3,scaleY(reScaleY(h/2+2)));
	g.drawLine(-shiftx+w-3,scaleY(reScaleY(h/2-2)),-shiftx+w-3,scaleY(reScaleY(h/2+2)));
	g.drawLine(-shiftx+w-w/4,scaleY(reScaleY(h/2-2)),-shiftx+w-w/4,scaleY(reScaleY(h/2+2)));
	g.drawLine(-shiftx+w/4,scaleY(reScaleY(h/2-2)),-shiftx+w/4,scaleY(reScaleY(h/2+2)));

	// Hash marks on vertical line
	g.drawLine(scaleX(reScaleX(w/2-2)),shifty+3,scaleX(reScaleX(w/2+2)),shifty+3);
	g.drawLine(scaleX(reScaleX(w/2-2)),shifty+h-3,scaleX(reScaleX(w/2+2)),shifty+h-3);
	g.drawLine(scaleX(reScaleX(w/2-2)),shifty+h/4,scaleX(reScaleX(w/2+2)),shifty+h/4);
	g.drawLine(scaleX(reScaleX(w/2-2)),shifty+h-h/4,scaleX(reScaleX(w/2+2)),shifty+h-h/4);

		// Draw Scaling
		g.setColor(new Color(200,200,200));
		g.drawString("0",scaleX(reScaleX(h/2))+2,scaleY(reScaleY(w/2))+11);
		
		try {
		g.drawString(""+correctScale(new BigDecimal(""+h/(factor*2.0)),
			1+Plot.c7.getSelectedIndex()),scaleX(reScaleX(w/2))+2,shifty+11);
		g.drawString(""+correctScale(new BigDecimal(""+w/(factor*-2.0)),
			1+Plot.c7.getSelectedIndex()),scaleX(reScaleX(0))+3,scaleY(reScaleY(w/2))+11);
		} catch(Exception e){System.out.println("Burp!!"+factor);}
	}

	public void drawEquation(Graphics g){
		g.setColor(Color.red);
		if (!showMe) 
			g.setColor(new Color(255,200,200));

		g.drawLine(0,scaleY(solveForY(reScaleY(shiftx))),w,scaleY(solveForY(reScaleY(shiftx+w))));
		g.drawLine(0,scaleY(solveForY_(reScaleY(shiftx))),w,scaleY(solveForY_(reScaleY(shiftx+w))));
	}

	// Draw Line2
	public void drawEquationFuzz(Graphics g){
		if (showMe) {
			g.setColor(new Color(200,255,200)); 
			double ne1,
				 ne2;
			ne1  = solveForY(reScaleY(shiftx));
			ne2 = solveForY(reScaleY(shiftx+h));
			int ld = Plot.c7.getSelectedIndex()+1;
			double diff = Math.pow(5,-ld+1);
			Polygon p = new Polygon();
			double dif = diff*Math.sqrt(getSlope()*getSlope()+1);
			p.addPoint(0,scaleY(ne1+dif));
			p.addPoint(0,scaleY(ne1-dif));
			p.addPoint(w,scaleY(ne2-dif));
			p.addPoint(w,scaleY(ne2+dif));

			g.fillPolygon(p);
			// Equation2

			ne1  = solveForY_(reScaleY(shiftx));
			ne2 = solveForY_(reScaleY(shiftx+w));
			dif = diff*Math.sqrt(getSlope_()*getSlope_()+1);

			p = new Polygon();
			p.addPoint(0,scaleY(ne1+dif));
			p.addPoint(0,scaleY(ne1-dif));
			p.addPoint(w,scaleY(ne2-dif));
			p.addPoint(w,scaleY(ne2+dif));
			g.fillPolygon(p);
		}
	}

	public void setEquation(double x, double y, double b, double x_, double y_, double b_){
		this.x = x;
		this.y = y;
		this.b = b;
		this.x_ = x_;
		this.y_ = y_;
		this.b_ = b_;
		setScale();
		repaint();
	}

	public double solveForX(double y1){
		double t = y*y1;
		t = b-t;
		return t/x;
	}

	public double solveForY(double x1){
		double t = x*x1;
		t = b-t;
		return t/y;
	}

	public double solveForX_(double y1){
		double t = y_*y1;
		t = b_-t;
		return t/x_;
	}

	public double solveForY_(double x1){
		double t = x_*x1;
		t = b_-t;
		return t/y_;
	}

	public double getSlope(){
		return -x/y;
	}

	public double getSlope_(){
		return -x_/y_;
	}

	public void setScale(){
		double big = Math.abs(solveForX(0));
		double uY  = Math.abs(solveForY(0));
		double uX_ = Math.abs(solveForX_(0));
		double uY_ = Math.abs(solveForY_(0));

		big = (uY  > big) ? uY  : big;
		big = (uX_ > big) ? uX_ : big;
		big = (uY_ > big) ? uY_ : big;

		if (z1 != 0 && z2 !=0){
			double z1a = Math.abs(z1);
			double z2a = Math.abs(z2);
			big = (z1a > big) ? z1a+z1a/8.0 : big;
			big = (z2a > big) ? z2a+z1a/8.0 : big;
		}
		factor = w/(2.0*big);
	}


	public void setScaleCenter(){
		shiftx = scaleX(z1)+w/2;
		shifty = scaleY(z2)+h/2;
		double big = Math.abs(solveForX(0));
		double uY  = Math.abs(solveForY(0));
		double uX_ = Math.abs(solveForX_(0));
		double uY_ = Math.abs(solveForY_(0));

		big = (uY  > big) ? uY  : big;
		big = (uX_ > big) ? uX_ : big;
		big = (uY_ > big) ? uY_ : big;

		if (z1 != 0 && z2 !=0){
			z1 = Math.abs(z1);
			z2 = Math.abs(z2);
			big = (z1 > big) ? z1+z1/8.0 : big;
			big = (z2 > big) ? z2+z1/8.0 : big;
		}
		factor = w/(2.0*big);
	}

	public int scaleX(double v){
		double value = v*factor;
		value += w/2.0;
		value -=shiftx;
		return (int)Math.round(value);
	}

	public int scaleY(double v){
		double value = v*factor;
		value = h/2.0 - value;
		value +=shifty;
		return (int)Math.round(value);
	}

	public double reScaleY(int v){
		double value = (v-(h/2.0));
		value = value/factor;
		return value;
	}

	public double reScaleX(int v){
		double value = v-w/2.0;
		value = (value*1.0)/factor;
		return value;
	}

	public boolean mouseDown (Event evt, int x, int y){
		//System.out.println("X: "+x+" y: "+y);
		//setScale();
		repaint();	
		return true;
	}

	public boolean keyDown (Event evt, int key){
		if (key == Event.UP) 
			shifty-=5;
		if (key == Event.DOWN) 
			shifty+=5;
		if (key == Event.LEFT) 
			shiftx+=5;
		if (key == Event.RIGHT) 
			shiftx-=5;
		if (key == Event.HOME){
			shiftx-=5;
			shifty-=5;
		}
		if (key == Event.PGUP){ 
			shiftx-=5;
			shifty-=5;
		}
		if (key == Event.END){
			shiftx+=5;
			shifty+=5;
		}
		if (key == Event.PGDN){ 
			shiftx-=5;
			shifty+=5;
		}
		//setScale();
		repaint();	
		return true;
	}

	public static BigDecimal correctScale(BigDecimal b,int sc){
		boolean stillZero = true;
		int x = b.toString().indexOf('.');
		if (x < 0)
			x = b.toString().length();

		b = b.movePointLeft(x);
		int ggg = slide(b);
		b = b.movePointRight(ggg);
		b = b.setScale(sc,BigDecimal.ROUND_HALF_EVEN);
		b = b.movePointLeft(ggg);
		b = b.movePointRight(x);
		return b;
	}

	public static int slide(BigDecimal b){
		int slideRight = 0;
		boolean stillZero = true;
		for (int i=b.toString().indexOf('.')+1;i<b.toString().length();i++){
			if (b.toString().charAt(i)=='0' && stillZero)
				slideRight++;
			else
				stillZero = false;
		}	
		return slideRight;
	}

	public Dimension getMinimumSize() {
		return new Dimension(w,h);
	}	// end of method minimumSize

	public Dimension getPreferredSize() {
		return new Dimension(w,h);
	}	// end of method preferredSize

} // End class
//
////////////////////////////////////////////////////////////////
//
class TextField2 extends TextField {
	Plot pete;

	public TextField2(int x, Plot pete){
		super(x);
		this.pete = pete;
	}

public boolean handleEvent(Event e){
	if (e.id == Event.KEY_PRESS){
		GraphPanel.showMe = false;
		pete.gp.repaint();
	}
	return super.handleEvent(e);
}
} // End class