如何使用 find_peak 函数 Python

如何解决如何使用 find_peak 函数 Python

我必须分析 PPG 信号。我找到了一些可以找到峰值的东西，但我无法使用高度值。它们像字典数组或其他东西一样存储，我不知道如何从中提取值。我尝试使用 dict.values() 但这没有用。

 import matplotlib.pyplot as plt
 import numpy as np
 from scipy.signal import savgol_filter
 
 data = pd.read_excel('test_heartpy.xlsx')
 arr = np.array(data)
 time = arr[1:,0]   # time in s 
 ECG = arr[1:,1]    # ECG
 PPG = arr[1:,2]    # PPG
 filtered = savgol_filter(PPG,251,3)

 plt.plot(time,filtered)
 plt.xlabel('Time (in s)')
 plt.ylabel('PPG')
 plt.grid('on')

PPG 信号看起来像 this。搜索我使用的峰值：

 # searching peaks
 from scipy.signal import find_peaks

 peaks,heights_peak_0 = find_peaks(PPG,height=0.2)
 heights_peak = heights_peak_0.values()
 plt.plot(PPG)
 plt.plot(peaks,np.asarray(PPG)[peaks],"x")
 plt.plot(np.zeros_like(PPG),"--",color="gray")
 plt.title("PPG peaks")
 plt.show()
 print(heights_peak_0)
 print(heights_peak)
 print(peaks)

印刷：

 {'peak_heights': array([0.4822998,0.4710083,0.43884277,0.46728516,0.47094727,0.44702148,0.43029785,0.44146729,0.43933105,0.41400146,0.45318604,0.44335938])}

 dict_values([array([0.4822998,0.44335938])])

 [787  2513  4181  5773  7402  9057 10601 12194 13948 15768 17518 19335]

突出显示峰值的信号看起来像 this。

解决方法

# the following will give you an array with the values of peaks
heights_peak_0['peak_heights'] 

# peaks seem to be the indices where find_peaks function foud peaks in the original signal. So you can get the peak values this way also
PPG[peaks]

heights_peak_0 是 scipy.signal.find_peaks

返回的属性字典

您可以找到有关返回内容的更多信息 here

您可以使用 heights_peak_0["peak_heights"]

提取包含所有峰高的数组 ,

根据docs，find_peaks() 函数返回由peaks 本身和properties dict 组成的元组。由于您只对峰值感兴趣，您可以简单地忽略元组的第二个元素而只使用第一个元素。

假设您想要获得峰的“坐标”，则可以像这样将峰高（y 值）与其位置（x 值）结合起来（基于 {{3 }}):

import matplotlib.pyplot as plt
from scipy.misc import electrocardiogram
from scipy.signal import find_peaks

x = electrocardiogram()[2000:4000]
peaks,_ = find_peaks(x,distance=150)

peaks_x_values = peaks
peaks_y_values = x[peaks]

peak_coordinates = list(zip(peaks_x_values,peaks_y_values))
print(peak_coordinates)

plt.plot(x)
plt.plot(peaks_x_values,peaks_y_values,"x")
plt.show()

印刷：

[(65,0.705),(251,1.155),(431,1.705),(608,1.96),(779,1.925),(956,2.09),(1125,1.745),(1292,1.37),(1456,1.2),(1614,0.81),(1776,0.665),(1948,0.665)]