2 Replies Latest reply on Nov 16, 2018 1:45 PM by Kate Srinivasan

    How Tableau decides what to include in the viz - related to # of marks at all?

    Kate Srinivasan
    Kate Srinivasan Nov 16, 2018 11:16 AM

      So I'm working through the learning modules online, and in particular was just watching "Additional Filtering Topics" which is part of the Visual Analytics topic. I notice (which is what they want us to see) in their example called ">$10k Sales", which puts SUM(Sales) on the Columns shelf and CustomerID on the Rows shelf, sorting Customer ID in descending order, that if I filter on an aggregated measure, say "SUM(Sales)" and filter for SUM(Sales) >= $10000 instead of filtering on CustomerID and using a "Condition" by field setting Sales Sum >= 10,000 and then if I add Category to the color shelf, that the viz decides to break a Customer ID's Sum of Sales down by Category, and so the filter I end up with is Sum of Sales for each category for each Customer ID. They do this to show us that if what we want is to see a customer's sales greater than $10,000 for all categories, the appropriate way to design the filter is to filter on CustomerID and use the condition by field setting Sales Sum >= 10,000.

       

      MY QUESTION IS: how does Tableau decide what marks to show in the viz? Is it a set calculation or based mostly on a proprietary algorithm to "make things look nice based on best practices"? Because in the first example of setting the filter on Sum(Sales), if instead I use the exact same setup but instead filter at a lesser sum of sales amount (say, Sum(Sales) >= $3000), I can get the viz to show me Customer IDs with Sum(Sales)>$3000 in either a single category or by combining two categories! If I reduce the filter to Sum(Sales)>=$1000 then the viz even shows me CustomerIDs with Sum(Sales)>$1000 in either one or combining two even up to three categories! What is going on here?... what exactly is Tableau showing me, because adding Category to the color shelf is NOT showing me CustomerIDs with Sum(Sales) > x in a single category like the learning video claims. The video says, "Tableau ran each mark past the filter" -- that makes sense to me, but how do I know what marks Tableau would be creating prior to running them past the filter, since there's not consistency here -- is this an arcane algorithm that is unknowable except to those who work at Tableau, or is there a simple computation I'm missing?

       

      Thanks

       

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        • 1. Re: How Tableau decides what to include in the viz - related to # of marks at all?
          Michael Gillespie
          Michael Gillespie Nov 16, 2018 12:14 PM (in response to Kate Srinivasan)

          You are misunderstanding what's going on. 

           

          In the video clip (your first image above), you have filtered the SUM of Sales to sales over $10,000.  That restricts the visible data to 6 customers, and each of those customers had sales in only ONE category.


          By placing the Category dimension on the Color mark, you are telling Tableau to use color to identify the Category that a customer's sales fall into.  5 of the customers ONLY had sales in the Technology category, and one had sales ONLY in the Office Supplies category.

           

          When you LOWERED the SUM of Sales threshold to whatever it is in the 2nd image, a larger number of customers show up, and it just so happens that all those NEW customers had sales in MULTIPLE Categories.  That is why Tableau is showing you 2 or 3 color divisions per bar.  The size of the color elements visually represents the dollar value of sales for Category.

           

          If you remove Category from the Color mark, you will get a single color bar for each customer, representing the total sales across all Categories.

          • 2. Re: How Tableau decides what to include in the viz - related to # of marks at all?
            Kate Srinivasan
            Kate Srinivasan Nov 16, 2018 1:45 PM (in response to Michael Gillespie)

            Hi Michael,

             

            Thanks for your answer. It's not just coincidence that the 6 customers with Sum(sales) > $10k also only had those sales in one category; that's actually the point of Tableau's exploration of this topic in the lesson. There are more CustomerIDs with Sum(Sales)>$10k in the underlying data. What they're trying to show is that if I filter on Sum(Sales) and then add Category to the color shelf, then sometimes Tableau will change at what level it's evaluating Sum(Sales) -- e.g. in those first screenshots I posted, Tableau started evaluating Sum(Sales) in a single category. However, my observation is that if I then lower the threshold evaluation amount for Sum(Sales), it is no longer even filtering forSum(Sales) in a single category, which I can tell because as I posted, Tableau begins to include Sum(Sales) over two or even over three categories.

             

            If what you're trying to explain is true "you have filtered the SUM of Sales to sales over $10,000.  That restricts the visible data to 6 customers, and each of those customers had sales in only ONE category.", then why is it any different when I filter the Sum(Sales) by using a conditional filter on CustomerID using the field Sales and saying >= 10,000? What appears in the first viz I posted is definitely not all CustomerID with sales over $10,000, that is what is visible in the lesson's other worksheet ">$10,000k Customer", or my reproduction of that here:

             

             

            Also, as a side note, sorry for leaving the reference line in the second viz I posted. It is extraneous and unrelated to the filter you can see in the top righthand corner.

            Thanks.