on matrix for power series cannot be made symmetric by
    scaling the basis, so this function differs from those for the
    orthogonal polynomials.

    Parameters
    ----------
    c : array_like
        1-D array of polynomial coefficients ordered from low to high
        degree.

    Returns
    -------
    mat : ndarray
        Companion matrix of dimensions (deg, deg).

    Notes
    -----

    .. versionadded:: 1.7.0

    rj