'Return a b-spline representing the derivative.
Parameters
nu : int, optional
Derivative order.
Default is 1.
Returns
b : BSpline object
A new instance representing the derivative.
See Also
splder, splantider'

def derivative(self, nu=1):

    c = self.c
    ct = (len(self.t) - len(c))
    if (ct > 0):
        c = np.r_[(c, np.zeros(((ct,) + c.shape[1:])))]
    tck = _fitpack_impl.splder((self.t, c, self.k), nu)
    return self.construct_fast(extrapolate=self.extrapolate, axis=self.axis, *tck)
