runge_stable_domain

代码说明：

  演示龙格库塔方法的绝对稳定区域，从1阶到4阶，且阶数可以调整。另外，区域的左右边界可以计算出来(Absolutely stable region demonstrates Runge-Kutta methods, from an order to the fourth order, and the order can be adjusted. Further, around the boundary region can be calculated)