2 Replies Latest reply on Oct 10, 2014 11:08 AM by Scott Tennican

    Forecast formula

    Mary Lee

      Does anyone has the actual forecast formula (in excel) for the 3 forecast methodologies: trend, seasonality and trend & seasonality? Reason being Tableau can do this at the aggregate level but not at individual customer level.  Workaround is to do this offline in excel and have Tableau connecting to the excel file to produce the visuals. Thanks.

        • 1. Re: Forecast formula
          Tracy Rodgers

          Hi Mary,


          After a quick search, I came across this site that goes into different ways of finding forecast with Excel


          Forecasting methods and formulas with Excel - Lokad:


          Hope it helps!



          • 2. Re: Forecast formula
            Scott Tennican

            If you want to forecast customer Sales, you will get a much better forecast if you aggregate before you forecast. The reason is that aggregate data is less variable and therefore more predictable. Also, the best forecasting methods require regular time series data as input which means that if you are doing a monthly forecast, your original data has values for sales during every month. A single customer is likely to produce a highly variable and irregular time series. You can partition your aggregate data in many ways in Tableau and still forecast. Also, Tableau forecasts are likely to be higher quality than the ones described in the website Tracy found because it selects the best of eight optimally parametrized exponential smoothing models. All exponential smoothing models assume that recent events are better predictors of future events than long ago events which is almost always true in practice. The simple linear regression or transformed linear regression models describe on that website weight the distant past equally with the more recent past.