def _get_rsv(df, n_days):
        """ Calculate the RSV (Raw Stochastic Value) within N days

        This value is essential for calculating KDJs
        Current day is included in N
        :param df: data
        :param n_days: N days
        :return: None
        """
        n_days = int(n_days)
        column_name = 'rsv_{}'.format(n_days)
        low_min = df['low'].rolling(
            min_periods=1, window=n_days, center=False).min()
        high_max = df['high'].rolling(
            min_periods=1, window=n_days, center=False).max()

        cv = (df['close'] - low_min) / (high_max - low_min)
        df[column_name] = cv.fillna(0).astype('float64') * 100
Calculate the RSV (Raw Stochastic Value) within N days

        This value is essential for calculating KDJs
        Current day is included in N
        :param df: data
        :param n_days: N days
        :return: None