How to make plot with datetime and scipy peaks in Python?

Question

I took one example from a question and I adapted it to my data set, but when it comes to making plots, I got stuck. I know how to make a date time + values plot, but I didn't figure out how can I make a combination.

The response I took is the following: Response.

The example has the following code:
Example Code:

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

np.random.seed(42)

# borrowed from @Majid Mortazavi's answer
random_number1 = np.random.randint(0, 200, 20)
random_number2 = np.random.randint(0, 20, 100)
random_number = np.concatenate((random_number1, random_number2))
np.random.shuffle(random_number)

peaks, _ = find_peaks(random_number, height=100)

plt.plot(random_number)
plt.plot(peaks, random_number[peaks], "x")
plt.show()

I adapted it to my real-values dataset and I have the following code:
Adapted Code:

peaks, _ = find_peaks(my_dataset['quality'], height=500)

plt.figure(figsize=(14,12))
x = my_dataset.index
y = my_dataset.quality
plt.scatter(x, y, s=1,c='b',label='quality')
plt.plot(peaks, my_dataset['quality'][peaks], "x")

plt.xlabel('datetime')
plt.ylabel('values')
plt.legend(loc='best')
plt.title('Qualities')
plt.show()

Initially, my code for plotting was this and it worked:
Initial Code:

plt.figure(figsize=(14,12))
x = my_dataset.index
y = my_dataset.quality
plt.scatter(x, y, s=1,c='b',label='quality')

plt.xlabel('datetime')
plt.ylabel('values')
plt.legend(loc='best')
plt.title('Qualities')
plt.show()

But I need to have the same plot, but with the "X" sign on the computed peaks.

So the final result should be something like this: (I edited the initial plot in paint for a visual idea of the final result)

I honestly do not know how to make it work. Can you please help me?

I highly appreciate any effort to help me!!! Thank you so much in advanced!

Answer 1

As documentation of scipy.signal.find_peaks reports:

Returns: peaks: ndarray
Indices of peaks in x that satisfy all given conditions.

Your peaks variable is an array of the indices of peaks. So, in order to access x and y coordinates of these peaks, you should replace:

plt.scatter(x, y, s=1,c='b',label='quality')
plt.plot(peaks, my_dataset['quality'][peaks], "x")

with

plt.scatter(x, y, s=1,c='b',label='quality')
plt.plot(x[peaks], y[peaks], "x")