Import RELEVANT data from the result files. Refer to the function
    :func:`reda.importers.sip04.import_sip04_data_all` for an importer that
    imports ALL data.

    Exported parameters:

    ================== ========================================================
    key                description
    ================== ========================================================
    a                  First current electrode
    b                  Second current electrode
    m                  First potential electrode
    n                  Second potential electrode
    frequency          Measurement frequency
    Temp_1             Temperature sensor 1 (optional)
    Temp_2             Temperature sensor 2 (optional)
    zt                 Complex Transfer Impedance (the measurement), mean value
    r                  Magnitude of mean measurements (=|zt|)
    rpha               Resistance phase [mrad]
    zt_1               Complex Transfer Impedance, first repetition
    zt_2               Complex Transfer Impedance, second repetition
    zt_3               Complex Transfer Impedance, third repetition
    ContactResistance  Contact resistance (mean value)
    ShuntResistance    Shunt resistance used [Ohm]
    ================== ========================================================

    Parameters
    ----------
    data_filename : string
        Path to .mat or .csv file containing SIP-04 measurement results. Note
        that the .csv file does not contain all data contained in the .mat
        file!

    Returns
    -------
    df : :py:class:`pandas.DataFrame`
        The data, contained in a DataFrame

def import_sip04_data(data_filename):
    """Import RELEVANT data from the result files. Refer to the function
    :func:`reda.importers.sip04.import_sip04_data_all` for an importer that
    imports ALL data.

    Exported parameters:

    ================== ========================================================
    key                description
    ================== ========================================================
    a                  First current electrode
    b                  Second current electrode
    m                  First potential electrode
    n                  Second potential electrode
    frequency          Measurement frequency
    Temp_1             Temperature sensor 1 (optional)
    Temp_2             Temperature sensor 2 (optional)
    zt                 Complex Transfer Impedance (the measurement), mean value
    r                  Magnitude of mean measurements (=|zt|)
    rpha               Resistance phase [mrad]
    zt_1               Complex Transfer Impedance, first repetition
    zt_2               Complex Transfer Impedance, second repetition
    zt_3               Complex Transfer Impedance, third repetition
    ContactResistance  Contact resistance (mean value)
    ShuntResistance    Shunt resistance used [Ohm]
    ================== ========================================================

    Parameters
    ----------
    data_filename : string
        Path to .mat or .csv file containing SIP-04 measurement results. Note
        that the .csv file does not contain all data contained in the .mat
        file!

    Returns
    -------
    df : :py:class:`pandas.DataFrame`
        The data, contained in a DataFrame

    """
    df_all = import_sip04_data_all(data_filename)
    columns_to_keep = [
        'a', 'b', 'm', 'n',
        'frequency',
        'Temp_1', 'Temp_2',
        'Zm_1', 'Zm_2', 'Zm_3',
        'Zg_m',
        'zt',
        'Rs',
        'r',
        'rpha',
    ]
    df = df_all[columns_to_keep]
    df = df.rename(columns={
        'Rs': 'ShuntResistance',
        'Zg_m': 'ContactResistance',
        'Zm_1': 'zt_1',
        'Zm_2': 'zt_2',
        'Zm_3': 'zt_3',
    })

    return df