Fourier

[BalzaniEdoardo]

Add a Fourier basis.

This PR adds a Fourier basis. The API is as follows:

import nemos as nmo
import numpy as np
import matplotlib.pyplot as plt

# this configuration exclude the 0 frequency creating 2*n_frequencies bases.
bas = nmo.basis.FourierEval(n_frequencies=5)
out = bas.compute_features(np.linspace(0, 1, 200))

plt.figure()
plt.title("No 0 frequency")
plt.plot(out)
plt.show()

# this configuration exclude the 0 frequency creating 2*n_frequencies bases + 1.
bas = nmo.basis.FourierEval(n_frequencies=5, include_constant=True)
out = bas.compute_features(np.linspace(0, 1, 200))

plt.figure()
plt.title("Include 0 frequency")
plt.plot(out)
plt.show()