// expo.java
// exponential growth
// adapted from a program in basic by H.T. Odum & E. Odum, 1994.

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

public class expo extends Applet
{
  double E, Q, K1, K4;
  Label l1, l2, l3, l4;
  TextField i1, i2, i3, i4;
  Button drawbutton;

  public void init()
  {
    l1 = new Label("E: "); i1 = new TextField("1",3); add(l1); add(i1);
    l2 = new Label("Q: "); i2 = new TextField("5",3); add(l2); add(i2);
    l3 = new Label("k1: "); i3 = new TextField("7",3); add(l3); add(i3);
    l4 = new Label("k4: "); i4 = new TextField("4",3); add(l4); add(i4);
    drawbutton = new Button("Draw");  add(drawbutton);
  }

  public boolean action(Event e, Object o)
  {
    E=(float)Integer.parseInt(i1.getText());
    Q=(float)Integer.parseInt(i2.getText());
    K1=(float)Integer.parseInt(i3.getText());
    K4=(float)Integer.parseInt(i4.getText());
    repaint();
	return true;
  }

  public void paint ( Graphics g )
  {
    int t;
    double DQ;
    t=0; DQ=0; K1=0.01f*K1; K4=0.01f*K4;
    g.drawRect(0,60,320,300);
    g.setColor(Color.green);
    do
    {
      if (360-Q>60) g.drawOval(t,(int)(360-Q),1,1);
      else g.drawOval(t,60,1,1);
      DQ=K1*Q*E-K4*Q;
      Q=Q+DQ;
      t=t+1;
    } while (t<=320);
   }
}
//Manuel Basler, October 24th 2000. Revised by Enrique Ortega 20-01-2001