/********************************
 * Class to plot the function   *
 ********************************/

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

public class Plotter extends Canvas {

    double x_min, x_max, y_min, y_max;
    double [] coefs = null;
    int [] x_points = null;
    int [] y_points = null;


    public Plotter() {
	super();

	Color myblue = new Color(10,10,100);
	setBackground(myblue);

	x_min = -100.0;
	x_max = 100.0;
	y_min = -100.0;
	y_max = 100.0;

	x_points = new int[100]; 
	y_points = new int[100]; 

    }

    public Dimension getPreferredSize() {
	return new Dimension(400,200);
    } 

    public void paint (Graphics g) {
             g.setColor(Color.white);
	     Dimension size = getSize();

	     int xo = (int) (size.width * (-x_min) / (x_max-x_min));
	     int yo = (int) (size.height * (-y_max) / (y_min-y_max));

             g.drawLine(0, yo, size.width, yo);
             g.drawLine(xo, 0, xo, size.height);
	     g.drawString("x", size.width-20, yo+20);
	     g.drawString("y", xo+10, 20);


	     /*******************************
	     for (int j=0; j<100; j++) {
		 g.drawString("|", xo+(10*j), yo+5);
	     }
	     for (int j=0; j<100; j++) {
		 g.drawString("-", xo, yo-(10*j));
	     }
	     ******************************/

	     
	     if (coefs != null) {
		 g.setColor(Color.yellow);
		 calcpoints();
		 g.drawPolyline(x_points, y_points, x_points.length);
	     }
    }

    public void calcpoints() {
	Dimension size = getSize();

	for (int i=0; i<x_points.length; i++) {
	    double x = i * (x_max - x_min) / x_points.length + x_min;
	    double y = 0.0;
	    for (int k=0; k<coefs.length; k++) {
		y = y*x + coefs[k];
	    }
	    x_points[i] = (int) (size.width * (x-x_min) / (x_max-x_min));
	    y_points[i] = (int) (size.height * (y-y_max) / (y_min-y_max));
	}
    } 
}