def get_data_df(column_head, resource):
    """Enables the user to download the data as a pandas dataframe indexed by UDN IDs (through API)
    Parameters : column_head (str): name of the header that will be selected. For example, if the columns that 
                                should be selected contain "this string", then column_head="this string".
                resource : picsure api resource
    Returns: df (pandas.core.Dataframe): dataframe indexed by UDN IDs of the selected columns
    """
    dictionary=resource.dictionary().find(column_head)

    query=resource.query()
    query.select().add(dictionary.keys())
    query.select().add('\\000_UDN ID\\')

    df=query.getResultsDataFrame()
    df.set_index("\\000_UDN ID\\", inplace=True)

    query.select().clear()

    return df