def liaupunov(x, fprime):
    """
    *x* is a very long trajectory from a map, and *fprime* returns the
    derivative of *x*.

    This function will be removed from matplotlib.

    Returns :
    .. math::

        \lambda = \\frac{1}{n}\\sum \\ln|f^'(x_i)|

    .. seealso::

        Lyapunov Exponent
           Sec 10.5 Strogatz (1994) "Nonlinear Dynamics and Chaos".
           `Wikipedia article on Lyapunov Exponent
           <http://en.wikipedia.org/wiki/Lyapunov_exponent>`_.

    .. note::
        What the function here calculates may not be what you really want;
        *caveat emptor*.

        It also seems that this function's name is badly misspelled.
    """

    warnings.warn("This does not belong in matplotlib and will be removed", DeprecationWarning) # 2009/06/13

    return np.mean(np.log(np.absolute(fprime(x))))