说明：  做信号处理的时候经常会用到FFT，而MATLAB自带的FFT只能变换出一列系数，想做成频谱图还要自己加一部分，自己写了一个小程序，输入原始信号和采样率，可以画出标准的幅值谱和功率谱。
(Do signal processing is often used when the FFT, and FFT MATLAB own transformation from a coefficient of only wanted to make Canada part of the spectrum but also their own, to write a small program, the input original signal and the sampling rate can be Draw a standard amplitude spectrum and power spectrum.)