'Computes the Vandermonde matrix.
Parameters
x : ndarray
input
params : throw away parameter
parameter list returned by non-linear fitters
Returns
result : ndarray
The Vandermonde matrix'

def fit_deriv(self, x, *params):

    v = np.empty((((self.degree + 1),) + x.shape), dtype=np.float)
    v[0] = 1
    if (self.degree > 0):
        v[1] = x
        for i in range(2, (self.degree + 1)):
            v[i] = (v[(i - 1)] * x)
    return np.rollaxis(v, 0, v.ndim)
