import numpy as np
from scipy.interpolate import interp1d
import matplotlib.pyplot as plt

data1 = np.loadtxt('inp_test_sp.txt', usecols=(0,1))
f = interp1d(data1[:,0], data1[:,1], kind='cubic')
xmin=-10.0
xmax=10.0
dx=0.1
ndx=int((xmax-xmin)/dx)+1
xnew = np.linspace(xmin,xmax,ndx)
for i in range(0,ndx):
    print(xnew[i],f(xnew[i]))
plt.plot(data1[:,0],data1[:,1],'ro',label='Observed')
plt.plot(xnew,f(xnew),'b-',label='cubic')
plt.legend()
plt.xlabel('$x$')
plt.ylabel('$y$ (python)')
plt.show()