Finding the x coordinate for the max value of y

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I have a function that is split in 3. (0 < x < L1) (L1 < x < a) (a < x L2).

I need to add a notation on the plot for the max value no matter where x is on the (0 < x < L2). I have:

c1 = np.arange(0,L1+0.1, 0.1) 
c2 = np.arange(L1,a+0.1, 0.1)
c3 = np.arange(a,L+0.1, 0.1)


y1 = -q*c1
y2 = -q*c2 + RAV
y3 = -q*c3 + RAV - P
fig, (ax1, ax2) = plt.subplots(2, 1, sharex=True)

ax1.fill_between(c1, y1)
ax1.fill_between(c2, y2)
ax1.fill_between(c3, y3)
ax1.set_title('S curve')

Mmax1=np.max(y1)
Mmax2=np.max(y2)
Mmax3=np.max(y3)
Mmax= round(max(Mmax1,Mmax2,Mmax3), 2)

Now I want to take find the x coordinate of the y value Mmax, but I don't know how to use something like x[np.argmax(Mmax)] where x = a.any(c1, c2, c3).

I need the x coordinate so that I can plot it in, where the value occurs 

ax2.annotate(text2,
                 xy=(max_x, Mmax), xycoords='data',
                 xytext=(0, 30), textcoords='offset points',
                 arrowprops=dict(arrowstyle="->"))

How can I fix it? Thank you!

matplotlib python
1 Answers

Here I would illustrate what may be useful for you,As I don't have you complete code to create your desire function I have defined 3 simple function with following description: by out_arr=np.maximum.reduce([y1,y2,y3]) we would have maximum in ever x and by result = np.where(out_arr == np.amax(out_arr)) we find out which index have maximum value. then maximum pint would be point=[Max_X,out_arr[Max_X]]

import matplotlib.pyplot as plt
import numpy as np

x= np.arange(0., 6., 1)
y1=x
y2=x**2
y3=x**3


out_arr=np.maximum.reduce([y1,y2,y3])
result = np.where(out_arr == np.amax(out_arr))
Max_X=result[0]
print(Max_X)

point=[Max_X,out_arr[Max_X]]

plt.plot(Max_X,out_arr[Max_X],'ro') 
# red dashes, blue squares and green triangles
plt.plot(x, y1, 'r--', x, y2, 'bs', x, y3, 'g^')
plt.show()

enter image description here

user_31039130
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