// coop.java
// cooperative existence
// adapted from a program in basic by H.T. Odum & E. Odum, 1994.

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

public class coop extends Applet
{
    Label pr1,pr2,pr3,pr4,pr5,pr6;
	TextField in1,in2,in3,in4,in5,in6;
	float q1,q2,qi1,qi2,q10,q20,k1,k2,k3,k4,k5,k6,k7,k8,t,ti,r,dq1,dq2,i;

    public void init()
    {
	    pr1 = new Label("Start value for Q1: ");
	    in1 = new TextField("8",4);
	    add(pr1);add(in1);
	    pr2 = new Label("Start value for Q2: ");
	    in2 = new TextField("8",4);
		add(pr2);add(in2);
		pr3 = new Label("Growth rate for Q1: ");
		in3 = new TextField("9",4);
		add(pr3);add(in3);
		pr4 = new Label("Growth rate for Q2: ");
		in4 = new TextField("5",4);
		add(pr4);add(in4);
		pr5 = new Label("Mortality rate for Q1: ");
		in5 = new TextField("5",4);
		add(pr5);add(in5);
		pr6 = new Label("Mortality rate for Q1: ");
		in6 = new TextField("5",4);
		add(pr6);add(in6);
	}

	public boolean action(Event e, Object o)
	{
	    q1 = (float)Integer.parseInt(in1.getText());
		q2 = (float)Integer.parseInt(in2.getText());
		k5 = 0.01f*(float)Integer.parseInt(in3.getText());
		k6 = 0.01f*(float)Integer.parseInt(in4.getText());
		k3 = 0.01f*(float)Integer.parseInt(in5.getText());
		k4 = 0.01f*(float)Integer.parseInt(in6.getText());
		repaint();
		return true;
	}

	public void paint (Graphics g)
	{
	     i=10;k1=0.08f;k2=0.04f;k7=0.002f;k8=0.002f;
		 q10=1;q20=1;t=0;ti=0;qi1=q1;qi2=q2;
		 g.drawRect(60,150,320,180);
		 while (t<319)
		 {
		     r=1/(1+k1*q1*q2-k2*q1*q2);
			 if (r<0) r=0;
			 dq1=k5*r*q1*q2-k7*q1*q2-k3*q1;
			 dq2=k6*r*q1*q2-k8*q1*q2-k4*q2;
			 q1+=dq1;
			 q2+=dq2;
			 t+=1;
			 g.setColor(Color.green);
			 g.drawLine((int)(60+ti),(int)(330-qi1*q10),(int)(60+t),(int)(330-q1*q10));
			 g.setColor(Color.red);
			 g.drawLine((int)(60+ti),(int)(330-qi2*q20),(int)(60+t),(int)(330-q2*q20));
			 ti=t;qi1=q1;qi2=q2;
		 }
	}
}
// Stefan Kontur & E. Ortega. September 2000