2 Replies Latest reply on Aug 15, 2018 5:40 PM by Patrick A Van Der Hyde

    Forecasting Issue

    Sonam  Malhotra

      Hi All,

       

      I am facing an issue in forecasting the data in the current sample book.

       

      I have dates from past 3 years and have records accordingly, now instead of sum, i want to do countdistinct the records and get the forecasting using past 3 years of data.

       

      Now, if i do month wise, i m getting the forecast results but i want to show it as per year not month, when i reduce it as per year, it shows no forecasted data due to short time series.

       

      The reason given in resolving the error for forecasting is, that it should be minimum 4 data points, now what does that mean? and if i can do that with sum why not with count distinct aggregation.

       

      Please help.

       

      Thanks,

      Sonam

        • 1. Re: Forecasting Issue
          Ankit Patel

          Hi Sonam,

           

          You are right Tableau does require at least five data points in the time series to estimate a trend, and enough data points for at least two seasons or one season plus five periods to estimate seasonality. For example, at least nine data points are required to estimate a model with a four quarter seasonal cycle (4 + 5), and at least 24 to estimate a model with a twelve month seasonal cycle (2 * 12).

           

          If you Drill it to Quarter level you can get the forecast for Distinct Count of Record as per example attached.

           

           

          Refer to How Forecasting Works in Tableau for further details:

          Getting More Data

          Tableau requires at least five data points in the time series to estimate a trend, and enough data points for at least two seasons or one season plus five periods to estimate seasonality. For example, at least nine data points are required to estimate a model with a four quarter seasonal cycle (4 + 5), and at least 24 to estimate a model with a twelve month seasonal cycle (2 * 12).

          If you turn on forecasting for a view that does not have enough data points to support a good forecast, Tableau can sometimes retrieve enough data points to produce a valid forecast by querying the datasource for a finer level of granularity:

          • If your view contains fewer than nine years of data, by default, Tableau will query the data source for quarterly data, estimate a quarterly forecast, and aggregate to a yearly forecast to display in your view. If there are still not enough data points, Tableau will estimate a monthly forecast and return the aggregated yearly forecast to your view.
          • If your view contains fewer than nine quarters of data, by default Tableau will estimate a monthly forecast and return the aggregated quarterly forecast results to your view.
          • If your view contains fewer than nine weeks of data, by default, Tableau will estimate a daily forecast and return the aggregated weekly forecast results to your view.
          • If your view contains fewer than nine days of data, by default, Tableau will estimate an hourly forecast and return the aggregated daily forecast results to your view.
          • If your view contains fewer than nine hours of data, by default, Tableau will estimate an minutely forecast and return the aggregated hourly forecast results to your view.
          • If your view contains fewer than nine minutes of data, by default, Tableau will estimate an secondly forecast and return the aggregated minutely forecast results to your view.

          These adjustments happen behind the scene and require no configuration. Tableau does not change the appearance of your visualization, and does not actually change your date value. However, the summary of the forecast time period in the Forecast Describe and Forecast Options dialog will reflect the actual granularity used.

          Tableau can only get more data when the aggregation for the measure you are forecasting is SUM or COUNT. See Data Aggregation in Tableau for information on available aggregation types and information on how to change the aggregation type.

           

          If you find this helpful, then please mark it accordingly. Thank you.

          • 2. Re: Forecasting Issue
            Patrick A Van Der Hyde

            Hello Sonam - the online help covers this topic - https://onlinehelp.tableau.com/v2018.1/pro/desktop/en-us/help.htm#forecast_resolve_errors.html?Highlight=forecast  

            You can change your data to quarters and get a forecast but the yearly data is too coarse.

             

            I suggest changing the data to include more values and the forecast will be more meaningful.

             

            Patrick