def size_scale(values, s_min, s_max):
    """

    Parameters
    ----------
    values : ndarray
        values to be displayed using the size of the scatter points
    s_min : float
        minimum value this set of values should be compared to
    s_max : float
        maximum value this set of values should be compared to

    Returns
    -------
    sizes : ndarray
        arbitrary scaling of values which should be appropriate for linearly scaled data and be visually distinct

    """
    return 30 + 200*(values-s_min)/(s_max-s_min)