def pot_rel(abs_df):
    """
    Return relative power per band, based on absolute power.
    :param abs_df: Dataframe with absolute power where rows are bands and columns are channels
    """
    rel_df = abs_df.copy()
    for col in abs_df:
        rel_df[col] = abs_df[col] / sum(abs_df[col])
    return rel_df