function predator_prey_continuous ( t0, tmax )

  tspan = [ t0, tmax ];

  y0 = [ 5000.0, 100.0 ];

  [ tout, yout ] = ode23 ( @pp_ode, tspan, y0 );

  plot ( tout, yout(:,1), 'g', ...
         tout, yout(:,2), 'r' );

  return
end
function dydt = pp_ode ( t, y )

  dydt(1,1) =    2.0 * y(1) - 0.001 * y(1) * y(2);
  dydt(2,1) = - 10.0 * y(2) + 0.002 * y(1) * y(2);

  return
end
