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),利用matlab写成的窄带噪声发生，可以得到很精确的幅值、频率、相位估计，基于kaiser窗的双谱线插值FFT谐波分析，代码里有很完整的注释和解释，对于初学matlab的同学会有帮助。
English Description：
This function is used to calculate any function of the first order partial derivative (numerical method), written using MATLAB narrowband noise can get very accurate amplitude, frequency and phase estimation, based on Kaiser window double spectrum line interpolation FFT algorithm for harmonic analysis, the code is very complete annotated and explained, for beginners matlab students have help.