I have a list as below:

freq = [29342, 28360, 26029, 21418, 20771, 18372, 18239, 18070, 17261, 17102]

I want to show the values of n-th and m-th element of the x-axis and draw a vertical line

plt.plot(freq[0:1000])

For example in the graph above, the 100th elements on the x-axis – how can I show the values on the line?

I tried to knee but it shows only one elbow. I suggest it is the 50th element? But what is exactly `x,y`

??

from kneed import KneeLocator kn = KneeLocator(list(range(0, 1000)), freq[0:1000], curve='convex', direction='decreasing') import matplotlib.pyplot as plt kn.plot_knee() #plt.axvline(x=50, color='black', linewidth=2, alpha=.7) plt.annotate(freq[50], xy=(50, freq[50]), size=10)

You might think that everybody knows this library `kneed`

. Well, I don’t know about others but I have never seen that one before (it does not even have a tag here on SO).

But their documentation is excellent (`qhull`

take note!). So, you could do something like this:

#fake data generation import numpy as np x=np.linspace(1, 10, 100) freq=x**(-1.9) #here happens the actual plotting from kneed import KneeLocator import matplotlib.pyplot as plt kn = KneeLocator(x, freq, curve='convex', direction='decreasing') xk = kn.knee yk = kn.knee_y kn.plot_knee() plt.annotate(f'Found knee at x={xk:.2f}, y={yk:.2f}', xy=(xk*1.1, yk*1.1) ) plt.show()

Sample output:

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