@classmethod
def _get_dmi(cls, df):
    """ get the default setting for DMI

        including:
        +DI: 14 days SMMA of +DM,
        -DI: 14 days SMMA of -DM,
        DX: based on +DI and -DI
        ADX: 6 days SMMA of DX
        :param df: data
        :return:
        """
    df['pdi'] = cls._get_pdi(df, cls.PDI_SMMA)
    df['mdi'] = cls._get_mdi(df, cls.MDI_SMMA)
    df['dx'] = cls._get_dx(df, cls.DX_SMMA)
    df['adx'] = df['dx_{}_ema'.format(cls.ADX_EMA)]
    df['adxr'] = df['adx_{}_ema'.format(cls.ADXR_EMA)]
