A colourful #WorkoutWednesday challenge this week, courtesy of Ann Jackson incorporating pie charts, top N functionality and interactivity and a highlight table. Pie charts can cause much debate amongst the data viz community and if this one was just representing the multitude of sub-categories, it certainly wouldn’t be ideal. But when the core aim is to simply present 2 key measures (those in the top N against the rest), the pie is a familiar and effective visual. In this instance, the outer ring segmenting all the sub-categories provides additional context without detracting from the main purpose of the viz.

So lets build…

• Creating the core calculations
• Building the Pie Chart
• Building the Highlight Table
• Adding the Interactivity

Creating the core calculations

First up, we’re going to need a parameter to define the ‘Top N’. Create an integer parameter with a range from 1 to 17, that steps every 1 interval, and is defaulted to 5.

pTopN

Next we’re going to use a Set to capture the Sub-Categories that are in the Top N Sales. Right click on Sub-Category -> Create ->Set. Use the Top tab to define a set captures the Sum of Sales that is based on the pTopN parameter.

Now, we want to create a grouping of those in and out of the set, which will be used as part of the highlight table

Sub-Cat Group

IF [Sub-Category Set] THEN ‘IN TOP ‘ + STR([pTopN])
ELSE ‘ALL ELSE’
END

Pop all these fields out into a table so you can see what’s going on as you change the pTopN parameter. Sort the Sub-Category by Sales descending.

Now we need to identify the % value of Sales for the Sub-Categories that are in the Top N (this is the label on the darker segment of the central pie chart), so for that we need

Total Sales

{FIXED:SUM([Sales])}

Top N Sales (in hindsight, this should have been named Sales per Group or similar)

{FIXED [Sub-Category Set] : SUM([Sales])}

Top N Sales %

IF ATTR([Sub-Category Set]) THEN
SUM([Top N Sales])/SUM([Total Sales])
END

Format this to percentage with 0 dp.

Adding to the table, we can see the values

The final field we need in order to build the pie, is an additional one to store the label text

Label:SubText

IF [Sub-Category Set] THEN ‘TOP ‘ + STR([pTopN]) END

Building the Pie Chart

To achieve this we’re going to build a dual axis pie chart, where one pie is used to define the In/Out of Top N segmentation in the centre, and the other pie is used to create the outer ring.

Create an axis by typing in MIN(0) onto the Rows shelf, and then adding another instance of MIN(0) next to it. This will generate 2 marks cards, which is where the fields to build the pie charts will be placed.

In the first MIN(0) marks card, change the mark type to Pie, then add Top N Sales to the Angle shelf and Sub-Category Set to the Colour shelf. Adjust colours to suit. Then add Top N Sales % and Label:SubText to the Label shelf. Adjust size of the view and the chart to suit. Also remove all text from the Tooltip.

Positioning the text is a bit fiddly. If you click on the text so the cursor changes to a cross symbol, you can then drag it to a better location. However, when you change the Top N parameter, the text will move. You can go through each parameter value and reposition the text each time (which I did.. it wasn’t too onerous for 17 values), however I found when published to Tableau Public, the positioning wasn’t honoured. Ann’s solution was the same, so I didn’t get too hung up on this, although if anyone resolved it, I’d love to know!

Now on the 2nd MIN(0) marks card, again change the mark type to Pie, and this time add Sales to the Angle shelf and Sub-Category to Colour. Sort the Sub-Category field by Sales descending. Additionally add Sub-Category Set to the Detail shelf (this will be needed later on to make the interactivity work). Edit the colour palette to use the Hue Circle options. Adjust the size of the pie chart. Adjust the tooltip too.

Now make the chart dual axis and synchronize the axis. If the colourful chart is displayed ‘on top’, then right click on the right hand axis and select move marks to back. Adjust the sizes of both pies, so the colour wheel is slightly larger than the other one.

Now hide the axis, and remove all borders and gridlines.

Building the Highlight Table

I’ve built the highlight table as a bar chart. Start off by adding Sub-Category Set, Sub-Cat Group and Sub-Category to Rows. Sort Sub-Category by Sales descending. Then type in MIN(1) into the Columns shelf.

Now add subtotals via the Analysis > Totals > Add all Subtotals menu. This adds 2 additional rows to each section

But we don’t want the ‘grand total’, so click on the Sub-Category Set context menu, and uncheck Subtotals

To position the totals at the top, go to Analysis > Totals > Column Totals To Top

Then add Sub-Category to the Colour shelf, and adjust the colour of the Total bar to white

We now need to get some text onto those bars, but we need some additional calculations to help up with this. Firstly, we want to get the rank of the Sub-Category. We’ll use a table calculation for this

Sales Rank

RANK(SUM([Sales]))

We also need a way to identify the Total rows differently from the main Sub-Categories. I referred to this Tableau KB for help here, and subsequently created

Size

SIZE()

To see what this is doing, add Size to the Label shelf, and adjust the table calculation setting to compute by all fields except the Sub-Category Set. The size of the total rows is 1.

Based on this logic, we can then create

LABEL:Bar

IF [SIZE]=1 THEN ‘SUBTOTAL FOR GROUP’
ELSE ‘#’+STR([Sales Rank]) + ‘ ‘ + ATTR([Sub-Category])
END

Add this to the Label shelf instead of the Size field and adjust the table calc settings as above. Align left. Then add Sales to the Label shelf too and adjust so its on the same row. Adjust the tooltip too.

Now hide the Sub-Category Set and the Sub-Category fields. Right click on the ‘IN TOP x’ text and Rotate Label, then click on Sub-Cat Group text and Hide Field Labels for Rows. Format the header text to suit.

Hide the MIN(1) axis, and set columns and gridlines to None. Adjust the Row dividers to be darker

Adding the Interactivity

Add the 2 sheets onto a dashboard, and add a Highlight Dashboard Action, that on Hover of either of the charts, it highlights the other chart based on the Sub-Category Set only.

I think that’s covered everything. My published viz is here.

Happy vizzin’! Stay Safe!

Donna