def filter_irr(df, irr_col, low, high, ref_val=None):
    """
    Top level filter on irradiance values.

    Parameters
    ----------
    df : DataFrame
        Dataframe to be filtered.
    irr_col : str
        String that is the name of the column with the irradiance data.
    low : float or int
        Minimum value as fraction (0.8) or absolute 200 (W/m^2)
    high : float or int
        Max value as fraction (1.2) or absolute 800 (W/m^2)
    ref_val : float or int
        Must provide arg when low/high are fractions

    Returns
    -------
    DataFrame
    """
    if ref_val is not None:
        low *= ref_val
        high *= ref_val

    df_renamed = df.rename(columns={irr_col: 'poa'})

    flt_str = '@low <= ' + 'poa' + ' <= @high'
    indx = df_renamed.query(flt_str).index

    return df.loc[indx, :]