中文说明：
该函数用来计算任意函数的一阶偏导数(数值方法),使用大量的有限元法求解偏微分方程，基于kaiser窗的双谱线插值FFT谐波分析。
English Description：
The function is used to calculate the first order partial derivative of any function (numerical method). A large number of finite element methods are used to solve the partial differential equations. The harmonic analysis of bispectral interpolation FFT based on Kaiser window