中文说明：
三次样条插值（简称Spline插值）是通过一系列形值点的一条光滑曲线，数学上通过求解三弯矩方程组得出曲线函数组的过程。本函数中采用第一类边界值。
English Description：
Cubic spline interpolation (spline interpolation for short) is a process of obtaining a set of curve functions by solving three moment equations through a series of smooth curves with shape value points. The first boundary value is used in this function.