# -*- coding: utf-8 -*-# 正弦信號的時域波形與頻譜圖import numpy as npimport matplotlib.pyplot as plimport matplotlibimport mathimport randomrow = 4col = 4N = 500fs = 5n = [2*math.pi*fs*t/N for t in range(N)]  # 生成了500個介于0.0-31.35之間的點# print naxis_x = np.linspace(0,3,num=N)#頻率為5Hz的正弦信號x = [math.sin(i) for i in n]pl.subplot(221)pl.plot(axis_x,x)pl.title(u'5Hz的正弦信號',fontproperties='SimHei')pl.axis('tight')#頻率為5Hz、幅值為3的正弦+噪聲x1 = [random.gauss(0,0.5) for i in range(N)]xx = []#有沒有直接兩個列表對應項相加的方式？？for i in range(len(x)):  xx.append(x[i]*3 + x1[i])pl.subplot(222)pl.plot(axis_x,xx)pl.title(u'頻率為5Hz、幅值為3的正弦+噪聲',fontproperties='SimHei')pl.axis('tight')#頻譜繪制xf = np.fft.fft(x)xf_abs = np.fft.fftshift(abs(xf))axis_xf = np.linspace(-N/2,N/2-1,num=N)pl.subplot(223)pl.title(u'頻率為5Hz的正弦頻譜圖',fontproperties='SimHei')pl.plot(axis_xf,xf_abs)pl.axis('tight')#頻譜繪制xf = np.fft.fft(xx)xf_abs = np.fft.fftshift(abs(xf))pl.subplot(224)pl.title(u'頻率為5Hz的正弦頻譜圖',fontproperties='SimHei')pl.plot(axis_xf,xf_abs)pl.axis('tight')pl.show()