中文说明：利用MATLAB的M文件进行FFT分析，需要设定数据步长，例子中数据来源于Excel文件。FFT分析后，将结果用图表显示，图表可设置横纵坐标的大小。
English Description：
Using Matlab m file for FFT analysis, we need to set the data step size. In the example, the data comes from excel file. After FFT analysis, the results are displayed in a chart, which can set the size of abscissa and ordinate.