Missing Numpy import?

[David-Herman]

Are you missing import for ones() ?

from numpy import array, hstack, zeros, linspace, pi, 
from numpy.linalg import solve
from scipy.integrate import odeint


in this cell

x0 = hstack(( 0, pi / 2 * ones(len(q) - 1), 1e-3 * ones(len(u)) )) # Initial conditions, q and u
t = linspace(0, 10, 1000)                                          # Time vector
y = odeint(right_hand_side, x0, t, args=(parameter_vals,))         # Actual integration

[moorepants]

Yes, I think it was reported in #5 also.