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

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

public class logistic extends Applet
{
    Label pr1,pr2,pr3;
	TextField in1,in2,in3;
	float ee,q,qi,k1,k4,dq,t,ti;

   public void init()
   {
    pr1 = new Label("Availability of constant-pressure source E: ");
	in1 = new TextField("17",4);
	add(pr1);add(in1);
	pr2 = new Label("Initial population Q (try up to 160): ");
	in2 = new TextField("4",4);
	add(pr2);add(in2);
	pr3 = new Label("Sensitiveness to crowding of the population: ");
	in3 = new TextField("8",4);
	 add(pr3);add(in3);
   }

   public boolean action (Event e, Object o)
   {
	ee = 0.1f*(float)Integer.parseInt(in1.getText());
	q = (float)Integer.parseInt(in2.getText());
	k4 = 0.0001f*(float)Integer.parseInt(in3.getText());
	repaint();
	return true;
   }

   public void paint (Graphics g)
   {
	 k1=0.04f;qi=q;t=0;ti=t;
	 g.drawRect(50,100,320,180);
	 while (t<320)
	 {
	  dq=k1*ee*q-k4*q*q;
	  q+=dq;
	  t+=1;
	  g.setColor(Color.orange);
	  g.drawLine((int)(50+ti),(int)(280-qi),(int)(50+t),(int)(280-q));
	  ti=t;qi=q;
	 }
   }
}
// Stefan Kontur & E. Ortega, 2000.