def import_sip04_data_all(data_filename):
    """Import ALL data from the result files

    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_all : :py:class:`pandas.DataFrame`
        The data, contained in a DataFrame
    """
    filename, fformat = os.path.splitext(data_filename)

    if fformat == '.csv':
        print('Import SIP04 data from .csv file')
        df_all = _import_csv_file(data_filename)
    elif fformat == '.mat':
        print('Import SIP04 data from .mat file')
        df_all = _import_mat_file(data_filename)
    else:
        print('Please use .csv or .mat format.')
        df_all = None

    return df_all