# Filter Challenge : How well do you know Tableau’s Order of Operations?

It was Erica Hughes’ turn to set the #WOW challenge this week. This ended up being a bit of a journey for me, because of one requirement – to use the max date of the dataset.

I typically use a FIXED LOD to determine the max date, which I did initially in this case, and after building a solution, tripped up when it came to adding some of the filters ‘to context’. The context filter meant my Max Date was changing depending on the filter and subsequently I wasn’t getting the right results for the ‘days since last purchase’.

So I ended up having to put my thinking cap back on, and after a lot of trial and error and reading on the internet (including this article by the Flerlage Twins) , I finally managed to get a solution that involved both LOD calculations (including a rarely used INCLUDE LOD) and Table calculations, and no context filters at all. This was a pretty complex solution. The table of data had to include the Order Date on the Detail shelf, resulting in multiple rows per customer showing, which meant I had to then use an INDEX()=1 filter to only show 1 row for each customer. I then used an additional INDEX() against each customer, so I could filter to show only the customers in position 1-10. My solution to this is published here.

After publishing, I checked Erica’s solution and found how she’d handled the max date requirement. It used a concept I haven’t had to use so far, so I decided to rebuild a less complex solution, which is what I will now blog about.

Capturing the max date of data set which isn’t affected by context filters

The usual way to define the maximum date in the data set is to create a FIXED LOD calculation, and this is still required

Max Date

{FIXED :MAX([Order Date])}

This returns 30 Dec 2021.

The problem is, once a context filter is applied to a sheet, the value of this field can change. For example, if Region is applied as a context filter and set to ‘South’, then what Tableau will do, based on the ‘order of operations’, is first filter all the data to just those records where Region=South. It will then work out the max date of these filtered records, and if there are no orders on 30 Dec 2021 for the South Region, then the value of the Max Date field will differ. This is because context filters get applied before FIXED LOD calculations. We need a way to ensure we can retain the 30 Dec 2021 without hardcoding it.

The solution is to use a parameter.

pMaxDate

A date parameter which is set to use the value of the Max Date field when the workbook is opened.

This is quite a sneaky but clever way to retain this, which is why I’m reworking my solution to use it, so I have something for future reference myself. When the workbook opens, the pMaxDate parameter will get set to 30 Dec 2021 and won’t ever change, whereas the Max Date field will change if context filters are used.

Building the Table

It may seem a bit odd, but I’m going to start with the table of data that’s displayed, as this requires the most calculations, and the most validation.

On a new sheet, add Customer Name, Customer ID to Rows and Sales onto Text. Order by Sales desc. Format Sales to \$ with 0dp.

We need to determine the latest order date for each customer in order to work out other information.

Latest Order Date

{FIXED [Customer ID] : MAX([Order Date])}

This finds the maximum Order Date for each Customer.

And with this, we can now work out

Days Since Last Purchase

DATEDIFF(‘day’, [Latest Order Date], [pMaxDate]

Note this is comparing the Latest Order Date to the pMaxDate parameter instead of Max Date.

Format this to custom number, with 0 dp and a suffix of ‘ days’.

Add Latest Order Date to Rows (exact date, discrete) and Days Since Last Purchase into the table.

Now we need to work out

Latest Order Amount

{FIXED [Customer ID]: SUM(IF [Order Date]=[Latest Order Date] THEN [Sales] END)}

For each customer, if the Order Date is the same as the Latest Order Date, then retrieve the Sales value.

Format this to \$ with 0 dp and add to the view.

Now add Customer ID to the Filter shelf and set to filter by the Top 10 based on Sales.

To validate the behaviour of the calculations add Region to the Filter shelf and select ‘South’. You’ll notice only 8 rows are shown, and not 10.

This is because the data has been filtered based on the top 10 customers with the most sales first, and then restricted those top 10, to those with sales in the South. Only 8 of the top 10 customers have sales in the South, hence the 8 rows.

To resolve this, we need to add Region to Context (right click on the filter and Add to Context . This has the effect of filtering all the data by Region = South first, and then displaying the top 10 customers by Sales. We now have 10 rows displayed.

Add State to the Filters shelf, and add that to context too. Test the table of results by selecting different combinations of regions and/or states and comparing to the results on Erica’s solution to verify all the calculations are behaving as expected.

Now we’re happy the table is displaying the data as expected, we can format it and make it ready for the dashboard :

• Remove Latest Order Date & Customer ID
• Set the Row Banding
• Set the Row Dividers to Level 0, so only row lines appear at top and bottom
• Remove Column Dividers
• Format all text (row/column headings & text data) to be 8pt.
• Alias Sales to be Total Sales (right click on the Sales title in the columns and Edit Alias)
• Remove Region & State from the Filter shelf. These will get re-added later.

Building the Map

On a new sheet, double click State to load a map (you may need to set your location to United States : Map menu -> Edit Locations).

Change mark type to a Filled Map, add Region to Colour and adjust colours.

Remove all map layers (Map menu -> Map Layers and uncheck all options listed on left hand side). Change border on Colour shelf to white.

Remove row & column dividers, and remove all map options (Map menu -> Map Options and uncheck all options).

Drag a new instance of State onto the canvas and Add a Marks Layer. This will create a 2nd marks card on the left. Change the colour of the circles to black. Add Sales to the Size shelf and adjust. Adjust the tooltip of both marks card (you’ll need to add Sales to the Tooltip on the map marks card).

Building the Legend

On a new sheet add Region to Columns and type in MIN(1) into the Columns shelf too. Add Region to the Label shelf, and the Colour shelf. Adjust the height of the rows, so you can see the text.

Edit the axis so it is fixed from 0 to 1. Then format the Label so the font is larger and centred.

Hide the axis and the Region (uncheck show header). Remove row & column dividers and any gridlines. Adjust the border on the Colour shelf to be white. Set the tooltip not to show.

Building the Bar Chart

On a new sheet, add Sub-Category to Rows and Sales to Columns. Order by Sales desc. Add Sub-Category to the Filter shelf and set to show Top 10 by Sales. Reduce the Size of the bars, and align the row labels to be left aligned, and the font to be 8.

Format the axis, so the values are displayed in \$K.

Hide the row label, and adjust Tooltip. You may need to create an additional calculated field based on Sales to add to the Tooltip which you can then format to \$ with 0dp.

Adding the interactivity & context filters

Add the sheets onto a dashboard. You’ll need to use a mixture of vertical & horizontal layout containers, inner and outer padding and background colours to get the required layout.

Add a dashboard filter action which runs on Select when the Legend sheet is selected, which affects all other sheets and shows all values when unselected.

Add another filter dashboard action, which this time runs on Select when the Map sheet is selected, which affects all sheets except the Legend sheet, and also shows all values when unselected.

Now click on one of the regions in the legend, then click on a state in the map. This has the effect of adding filters to the shelves on the other sheets. Navigate to the Table sheet, and add the 2 ‘Action’ filters to context

Do the same for the Bar char sheet.

And you should now have a completed viz. My published version based on this solution is here.

Happy vizzin’!

Donna