周期函数傅里叶级数展开相关的函数M文件，Fouriers( )、Fouriers2( )分别为非分段和分段函数的部分和（n阶），Fouriersp( )Fouriersp2( )为相应的的3阶、5阶、10阶傅里叶逼近，piecewise( )为分段函数-Fourier series expansion of periodic functions related function M-files, Fouriers (), Fouriers2 () functions, respectively, for non-segmented and segmented portion and (n-order), Fouriersp () Fouriersp2 () for the corresponding third-order , five bands, 10 fourier approximation, piecewise () is piecewise