plot specific values on a plot

Question

I got this plot out of a matplotlib plot.

My code is shown here:

from os import sep
import pandas as pd
import matplotlib.pyplot as plt
import numpy as np
from pathlib import Path
from numpy.fft import rfft, rfftfreq



    
dt=1/10000
    
g=pd.read_csv('20210803-0002.csv', sep = ';', skiprows=[1,2],usecols = [4],dtype=float, decimal=',')
    
n=len(g)
   
acc=g.values.flatten() #to convert DataFrame to 1D array
    #acc value must be in numpy array format for half way mirror calculation

fft=rfft(acc)*dt
freq=rfftfreq(n,d=dt)

FFT=abs(fft)

plt.plot(freq,FFT,label = 'neuer Motor')

plt.legend()    


plt.show()
plt.close()

I would like to add a marker for every y value > 10.

Does any of you know how to plot these values on the graph?

Answer 1

You can set your treshold and use it to create a filter:

threshold = 40
filt = y > threshold

Then you can filter x and y values:

ax.plot(x, y)
ax.plot(x[filt], y[filt], marker = 'o', linestyle = '')

Complete Code

import numpy as np
import matplotlib.pyplot as plt

N = 1000
x = np.linspace(0, 3000, N)
y = 50*np.random.rand(N)


threshold = 40
filt = y > threshold


fig, ax = plt.subplots()

ax.plot(x, y)
ax.plot(x[filt], y[filt], marker = 'o', linestyle = '')

plt.show()