private static List <Point> DataToMonthly(List <Point> data) { /* if data is monthly return data, if data is daily process * data, otherwise print error message and get out of here */ if (Utils.IsDataMonthly(data)) { return(data); } else if (Utils.IsDataDaily(data)) { return(DailyToMonthly(data)); } else { Console.WriteLine("error: only monthly or daily inputs supported"); return(new List <Point> { }); } }