I am a newbie here. well I am trying to find a method or a formula to forecast meals per day, which have ̀5 meals to upload on flights, sales, wastage and passengers are what I have to consider, the old template is not completed yet , and its not so good to forecast, and I can't think of other formulas or methods to forecast , I have the sales in the past few months.. anyone can suggest me which methods can solve this problem? well I am using MS.Excel to calculate or if there is a program to suggest me it would be great :) ..thanks a lot for helping and sorry for my bad english :)
I'd suggest taking a look at http://www.amazon.com/Predictive-Analytics-Microsoft-Conrad-Carlberg/dp/0789749416 if you are restricted to Excel. There are also example R codes in the book to help transition from thinking in Excel to thinking in R. The spreadsheet examples from the book can be found here: http://www.quepublishing.com/store/predictive-analytics-microsoft-excel-9780789749413. Chapter 5 is about time series.
I don't believe that you will find a soultion in EXCEL. If you look at Forecasting hourly time series with daily, weekly & annual periodicity you will find an interesting discussion of daily forecasting. The referenced question also includes hourly forecasting issues which you can safely ignore as you are just concerned with daily activity.
You can use in-built Excel functionality:
or an external tool, e.g.