Capture points and replot with cubic interpolation

_coords.npy

capture_points.py

import os
import matplotlib.pyplot as plt
import numpy as np
from scipy import interpolate, optimize

DATA = '/tmp/_coords.npy'
N = 1000
P = 9

if os.path.exists(DATA):
    data = np.load(DATA)
else:
    plt.xlim([1, 7])
    plt.ylim([1, 4])
    plt.grid()
    data = plt.ginput(n=-1)
    np.save(DATA, data)

p = interpolate.CubicSpline(data[:, 0], data[:, 1])
p_min = optimize.fmin(p, x0=3)
p_opt = p(p_min)

x, y = data.T
x_min, x_max = x.min(), x.max()
t = np.linspace(x.min(), x.max(), N, endpoint=True)
plt.plot(x, y, 'x', color='red')
plt.annotate(
    'Some text', xy=[p_min, p_opt],
    arrowprops={'arrowstyle': '->', 'connectionstyle': 'arc3,rad=-.2'},
    xytext=[p_min + 0.7, p_opt + 0.1]
)
plt.hlines(2.5, x_min, x_max)

plt.plot(t, p(t))
plt.show()