akima / pchip

gistfile1.txt

from scipy.interpolate import Akima1DInterpolator as Akima
from scipy.interpolate import PchipInterpolator as pchip
from scipy.interpolate import CubicSpline as cubic
import numpy as np
import matplotlib.pyplot as plt

plt.ion()
np.random.seed()

def show_plot(x, y):
    p = pchip(x, y)
    c = cubic(x, y, bc_type='natural')
    c2 = cubic(x, y)
    a = Akima(x, y)

    xp = np.sort(x[0] + (x[-1] - x[0])*np.random.random(200))
   
    plt.plot(x, y, 'b+', ms=8, mec='r')
    plt.plot(xp, c(xp), 'y-', lw=3, alpha=0.7)     # yellow for Cubic/natural
    plt.plot(xp, c2(xp), 'y-', lw=3, alpha=0.3)    # light-yellow for Cubic/not-a-knot
    plt.plot(xp, a(xp), 'b-', lw=2, alpha=0.5)     # light-blue for Akima
    plt.plot(xp, p(xp), 'm-', lw=1, alpha=1)       # red for pchip
    plt.draw()

x = range(20)
y = 10 * np.sort(np.random.random(20))
show_plot(x, y)

x = range(20)
y = 10 * np.random.random(20)
show_plot(x, y)

x = 10 * np.sort(np.random.random(20))
y = 10 * np.sort(np.random.random(20))
show_plot(x, y)

x = 10 * np.sort(np.random.random(20))
y = 10 * np.random.random(20)
show_plot(x, y)