Return the natural log of growth.

    See also
    --------
    :func:`growth`

def ln_growth(eqdata, **kwargs):
    """
    Return the natural log of growth.

    See also
    --------
    :func:`growth`
    """
    if 'outputcol' not in kwargs:
        kwargs['outputcol'] = 'LnGrowth'
    return np.log(growth(eqdata, **kwargs))