CODEWITHSUNDEEP
pythonscipy
testStackFlow
testStackFlow

Reputation: 49

Finding peaks above threshold

I am using from scipy.signal import find_peaks. Is it possible to find all peaks greater than the specified threshold. I am not completley certain if you can do this. For example: indices = find_peaks(s_volts, threshold= 0.5*maxPeak) I am trying to find all peaks that are greater than 50% of the max peak.

Upvotes: 0

Views: 3443

Answers (2)

rafa
rafa

Reputation: 255

If you can define your threshold value beforehand you can use the height argument. Borrowing from @omer-tuchfeld example:

from scipy.signal import find_peaks
import numpy as np
from matplotlib import pyplot as plt

x = np.array([1,2,3,2,1,2,3,2,1,2,3,4,3,2,1,2,3,4,7,4,3,2,1])

threshold = 0.5 * max(x)
peaks_indices = find_peaks(x, height=threshold)[0]
peaks_values = x[peaks_indices]

fig = plt.figure()
plt.plot(range(len(x)), x)
for index in peaks_indices:
    plt.axvline(index)

plt.axhline(threshold)
plt.scatter(peaks_indices, peaks_values, s=200)
plt.show()

Upvotes: 1

Omer Tuchfeld
Omer Tuchfeld

Reputation: 3022

Don't think there's a built-in way to do that. Here's how you can go about it without scipy:

from scipy.signal import find_peaks
import numpy as np
x = np.array([1,2,3,2,1,2,3,2,1,2,3,4,3,2,1,2,3,4,7,4,3,2,1])
peaks_indices = find_peaks(x)[0]
peaks = np.array(list(zip(peaks_indices, x[peaks_indices])))
threshold = 0.5 * max(x[peaks_indices])
filtered_peaks = [(index, value) for index, value in peaks if value > threshold]

# If you just want the indices:
filtered_peaks_indices = [index for index, value in peaks if value > threshold]

# Or just want the values
filtered_peaks_values = [value for index, value in peaks if value > threshold]

# Visualize
from matplotlib import pyplot as plt
plt.plot(range(len(x)), x)
for index in peaks_indices:
     plt.axvline(index)

plt.axhline(threshold)
plt.scatter(filtered_peaks_indices, filtered_peaks_values, s=200)
plt.show()

Upvotes: 2

Related Questions