def results_summary(results_data):
    """
    Return a summary of the results stored in a dataframe.
    Returns a dict containing unique entities in each column
    Ignores the exp_data, f_min, min_params and time columns
    """
    
    unique_vals_dict = {}
    
    col_list = list(results_data.columns.values)
    for col in col_list:
        if col in ['exp_data', 'f_min', 'min_params', 'time']:
            continue
        
        uniques_temp_list = results_data[col].unique()
        unique_vals_dict[col] = list(uniques_temp_list)
    
    return unique_vals_dict