如何繪製2個動畫圖形與x軸固定在matplotlib與subplots？

Question

該程序的目的：我需要在頂部繪製一個信號圖形，並在底部繪製該信號的光譜圖形，只有兩種情況下的y數據會有所不同。

我在輸入上產生一個隨機噪聲的正弦波，並將其繪製在頂部，這是正常工作。

問題是當我嘗試繪製頻譜圖時。由於某些原因，它並未更新，我也不太瞭解matplotlib.animation.FuncAnimation的功能。

代碼：

import numpy as np 
import matplotlib.pyplot as plt 
import matplotlib.animation as animation 

dt = 0.01 
Fs = 44000.0    # sample rate 
timestep = 1.0/Fs   # sample spacing (1/sample rate) 
t = np.arange(0, 10, dt) # t range 
n = 256     # size of the array data 
w = 10000     # frequency of the input 

data = np.sin(2*np.pi*w*t) 



def update(data): 
    # update the curves with the incoming data 
    line.set_ydata(data) 
    #line2.set_ydata(magnitude) 

    return line, 

def generateData(): 
    # simulate new data coming in 
    while True: 
     nse = np.random.randn(len(t)) 
     r = np.exp(-t/0.05) 
     cnse = np.convolve(nse, r)*dt 
     cnse = cnse[:len(t)] 
     data = np.sin(2*np.pi*w*(t)) + cnse 
     magnitude = np.fft.fft(data)/n 
     magnitude = np.abs(magnitude[range(n//2)]) 
     yield data 

fig = plt.figure() 

# plot time graph axis 
timeGraph = plt.subplot(2, 1, 1) 
timeGraph.set_ylim(-0.2, 0.2) 
timeGraph.set_xlabel('Time') 
timeGraph.set_ylabel('Amplitude') 

# plot frequency graph axis 
freqGraph = plt.subplot(2, 1, 2) 
freqGraph.set_xlabel('Freq (Hz)') 
freqGraph.set_ylabel('|Y(freq)|') 

# get frequency range 
n = len(data) # length of the signal 
print(len(data)) 
k = np.arange(n) 
T = n/Fs 
freq = k/T # two sides frequency range 
freq = freq[range(n//2)] # one side frequency range 

# fft computing and normalization 
magnitude = np.fft.fft(data)/n 
magnitude = np.abs(magnitude[range(n//2)]) 


line, = timeGraph.plot(np.linspace(0, 1, len(t)), 'b') 
line2, = freqGraph.plot(freq, magnitude, 'g') 


# animate the curves 
ani = animation.FuncAnimation(fig, update, generateData, 
           interval=10, blit=True) 

plt.show() # open window 

獎金：我怎麼初始化數據和幅度是否正確？

Answer 1

爲了同時更新時間和頻率圖，需要將數據從兩者都設置爲update函數中的相應圖。當然你也需要在生成函數中提供這些數據。所以生成函數應該爲yield (data, magnitude)，更新函數應該接受這個元組作爲輸入。

爲頻率圖設置一些限制也是一個好主意，freqGraph.set_ylim([0, 0.006])這樣它就不會空着。

我不知道你的意思是我該如何正確初始化數據和幅度？。我認爲他們是正確初始化的，因爲它們是針對每一幀進行計算的，包括第一幀。

這裏是一個工作代碼。

import numpy as np 
import matplotlib.pyplot as plt 
import matplotlib.animation as animation 

dt = 0.01 
Fs = 44000.0    # sample rate 
timestep = 1.0/Fs   # sample spacing (1/sample rate) 
t = np.arange(0, 10, dt) # t range 
n = 256     # size of the array data 
w = 10000     # frequency of the input 

data = np.sin(2*np.pi*w*t) 



def update(data): 
    # update the curves with the incoming data 
    line.set_ydata(data[0]) 
    line2.set_ydata(data[1]) 
    return line, line2, 

def generateData(): 
    # simulate new data coming in 
    while True: 
     nse = np.random.randn(len(t)) 
     r = np.exp(-t/0.05) 
     cnse = np.convolve(nse, r)*dt 
     cnse = cnse[:len(t)] 
     data = np.sin(2*np.pi*w*(t)) + cnse 
     magnitude = np.fft.fft(data)/n 
     magnitude = np.abs(magnitude[range(n//2)]) 
     yield (data, magnitude) 

fig = plt.figure() 

# plot time graph axis 
timeGraph = plt.subplot(2, 1, 1) 
timeGraph.set_ylim(-0.2, 0.2) 
timeGraph.set_xlabel('Time') 
timeGraph.set_ylabel('Amplitude') 

# plot frequency graph axis 
freqGraph = plt.subplot(2, 1, 2) 
freqGraph.set_ylim([0, 0.006]) 
freqGraph.set_xlabel('Freq (Hz)') 
freqGraph.set_ylabel('|Y(freq)|') 

# get frequency range 
n = len(data) # length of the signal 
print(len(data)) 
k = np.arange(n) 
T = n/Fs 
freq = k/T # two sides frequency range 
freq = freq[range(n//2)] # one side frequency range 

# fft computing and normalization 
magnitude = np.fft.fft(data)/n 
magnitude = np.abs(magnitude[range(n//2)]) 


line, = timeGraph.plot(np.linspace(0, 1, len(t)),'b') 
line2, = freqGraph.plot(freq, magnitude,'g') 


# animate the curves 
ani = animation.FuncAnimation(fig, update, generateData, 
           interval = 10, blit=True) 

plt.show() # open window