// compete.java
// competition of two populations in exponential growth (with quadratic feedback)
// adapted from a program in basic by H.T. Odum & E. Odum, 1994

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

public class compete extends Applet
{

 Label prompt1, prompt2, prompt3, prompt4, prompt5, prompt6, prompt7;
 TextField input1, input2, input3, input4, input5, input6, input7;
 Button drawbutton;
 double Q1, Q2, K1, K2, K3, K4, E, Q1i, Q2i, D1, D2, t, ti, R;
 int a;

 public void init()
 {
 	prompt1 = new Label("Initial Population Q1: ");
	input1 = new TextField("3", 4);
	add(prompt1); add(input1);

	prompt2 = new Label("Initial Population Q2: ");
	input2 = new TextField("3", 4);
	add(prompt2); add(input2);

	prompt3 = new Label("K1 Growth rate of Q1: ");
	input3 = new TextField("7", 4);
	add(prompt3); add(input3);

	prompt4 = new Label("K2 Growth rate of Q2: ");
	input4 = new TextField("8", 4);
	add(prompt4); add(input4);

	prompt5 = new Label("K3 Mortality rate of Q1: ");
	input5 = new TextField("5", 4);
	add(prompt5); add(input5);

	prompt6 = new Label("K4 Mortality rate of Q2: ");
	input6 = new TextField("5", 4);
	add(prompt6); add(input6);

	prompt7 = new Label("Quadratic feedback (1/0)?: ");
	input7 = new TextField("0", 4);
	add(prompt7); add(input7);

	drawbutton = new Button("Draw");
	add(drawbutton);
 }

 public boolean action(Event e, Object o)
 {
 	Q1 = (float)Integer.parseInt(input1.getText());
 	Q2 = (float)Integer.parseInt(input2.getText());
	K1 = 0.01f*(float)Integer.parseInt(input3.getText());
	K2 = 0.01f*(float)Integer.parseInt(input4.getText());
	K3 = 0.01f*(float)Integer.parseInt(input5.getText());
	K4 = 0.01f*(float)Integer.parseInt(input6.getText());
	a = Integer.parseInt(input7.getText());
 	repaint();
 	return true;
 }

 public void paint(Graphics g)
 {
 	g.drawRect(0,120,320,180);
	t=0; ti=0; E=1;

 	while (t<320)
 	{
		ti=t+1;
		R=E/(1+K1*Q1-K3*Q1);
		if (a == 0) D1=K1*E*Q1-K3*Q1;
		else if (a == 1) D1=K1*R*Q1*Q1-K3*Q1;
		D2=K2*E*Q2-K4*Q2;
		Q1i=Q1+D1;
		Q2i=Q2+D2;
		if (Q1i<=180) {
			g.setColor(Color.green);
			g.drawLine((int)t, (int)(300-Q1), (int)ti, (int)(300-Q1i));}
		if (Q2i<=180) {
			g.setColor(Color.blue);
			g.drawLine((int)t, (int)(300-Q2), (int)ti, (int)(300-Q2i));}
			t=ti;Q1=Q1i;Q2=Q2i;}
 	}
}
// Manuel Basler & E. Ortega, October 17th 2000