1 Reply Latest reply on Feb 19, 2014 10:33 AM by medwin chang

    Forcasting and Trendlines

    Tarryn Balsdon

      Hi all,

       

      I have a large set of data with daily expenditure along different lines. I want to make a prediction about the total expenditure of a line at the end of the month (/year). Ultimately I would like to show the running total of the expenditure, with this prediction extending from it, against a running total of our budget.

       

      When I tried forecasting I was unable to forecast against a table calculation (running total, and could not show an additive forecast from month to date total). The help menu said I needed to create a version of the view that does not contain a table calculation. How can I do this (without changing the raw data?)?

       

      I have also tried using trend lines, but they come out skewed (I think because my raw data extends to dates beyond that of this particular line - so that I can examine multiple lines that occur across different dates) and I am unable to click the "Force Y-intercept to 0" box, which I think would solve my problems...

       

      Any suggestions would be most welcome!

       

      Thanks!

        • 1. Re: Forcasting and Trendlines
          medwin chang

          Tarryn,

           

          I have also encountered the same problem of the option "force y-intercept to zero" being greyed out. I believe I might have found a "solution" to the issue (though this might be something that tableau will fix in future versions). The option will be greyed out if the fields that you are plotting are not Measures (namely the columns and rows cannot be Dimension or Attribute type data).

           

          To get around the issue, temporarily make your fields into Measures type (and tableau will automatically sum the fields by default - don't worry about that for now), add the trendline then edit the trendline. At this point, the option for "forcing y-intercept to zero" should be available for selection. Once the option is turned on, it will force the trend line to intercept at 0. At this point you can change your fields back to the desired data type. If you try to edit your trendline now, the option will be greyed out again, but the intercept should still remain at zero.

           

          Hope this helps!