def RCI_calc(mutual_information, reference_entropy):
    """
    Calculate RCI (Relative classifier information).

    :param mutual_information: mutual information
    :type mutual_information : float
    :param reference_entropy: reference entropy
    :type reference_entropy : float
    :return:  RCI as float
    """
    try:
        return mutual_information / reference_entropy
    except Exception:
        return "None"