def _rational_conversion(vector, cc_val):
    """ apply rational conversion to data

    Parameters
    ----------------
    vector : numpy 1D array
        raw data to be converted to physical value
    cc_val : mdfinfo4.info4 conversion block ('CCBlock') dict

    Returns
    -----------
    converted data to physical value
    """
    p1 = cc_val[0]
    p2 = cc_val[1]
    p3 = cc_val[2]
    p4 = cc_val[3]
    p5 = cc_val[4]
    p6 = cc_val[5]
    return (p1 * vector * vector + p2 * vector + p3) / (p4 * vector *
        vector + p5 * vector + p6)
