Can you do Comparative Quantity Analysis?

For this week’s challenge, Sean wanted to test us on a particular aspect of Tableau – the use of INCLUDE & EXCLUDE LOD expressions, although he then finished off the challenge intro with the statement “You can complete this challenge however you like but just DON’T USE A FIXED LOD”.

Like many, I am pretty comfortable using a straightforward FIXED LoD, but rarely get INCLUDE & EXCLUDE ‘out of my toolbox’. I usually end up using them because I’ve followed an example online to achieve a specific task. With this challenge, I had every intention of trying to make use of these ‘lesser used’ LoDs when I started out.

However I did struggle. I got to a point where I knew what I’d do with table calculations, but however I tried with various LoD statements, I couldn’t get the behaviour I desired. And at this point, I had a working solution that hadn’t used FIXED LoDs either, so based on Sean’s closing statement, I had achieved a result. When doing these challenges, I do have to consider how much of my time to devote to them (although COVID restrictions does mean my home/family/social life if not as busy at the moment), so I chose to publish so I could feel content I had completed the challenge. However, there was a niggle, that I hadn’t managed to apply the functions the challenge was really testing for.

A twitter post the next day from a fellow #WOW participant Nik Eveleigh, calling out how helpful Tim Ngwena‘s Include LoD YouTube video was, piqued my interest, and that evening I set about watching the video, and subsequently managing to create another solution using the required INCLUDE & EXCLUDE LoDs, without any table calculations either.

So for this blog, you’re gonna get two solutions 🙂 I’ll explain the various fields required for each solution, and build out a tabular view to demonstrate. Building the view is then pretty much the same.

  • Getting Started
  • The Table Calculation Solution
  • The LoD Solution
  • Building the Viz
  • Adding the dashboard interactivity

Getting Started

First up, just a note about the data set. You need to use the Superstore dataset, but need a version that includes the Manufacturer field. This doesn’t seem to exist by default in the excel file included as part of Tableau’s install. So I used the data provided by Sean on data.world.

Secondly, once connected to the data source, we’re going to need a parameter that is ultimately going to be used to drive the dashboard interactivity later on. The parameter needs to store the value of the Sub-Category the user has selected on the chart. The parameter is required regardless of which solution you choose to follow.

pSelectedSubCat

This is a string parameter that contains the text Fasteners by default. Create this and then show it on the view.

The Table Calculation Solution

The first measure being displayed on the viz is the average Quantity by Manufacturer for each Sub-Category; that is for the total quantity of goods sold against each sub-category, how much on average did each manufacturer order?

Count Manufacturer

COUNTD([Manufacturer])

Identifies the distinct number of manufacturers

Avg Qty

SUM([Quantity])/[Count Manufacturer]

Lets put these fields out into a table, so we can see the values. I’ve sorted the rows by Avg Qty descending, and you can see the values match the required output.

Now we need to identify the Avg Qty associated to the selected Sub-Category.

Selected Avg

IF [pSelectedSubCat]=MIN([Sub-Category]) THEN [Avg Qty] ELSE 0 END

This will return the value we want for the row that matches the value of the parameter, and 0 otherwise. The Sub-Category dimension is wrapped in MIN as Avg Qty is an aggregated value, so the dimensions also need to be aggregated. MAX or ATTR will work as well.

Pop this field onto the table.

For the next step, we need to find a way to ‘replicate’ this 152 value across all the rows displayed. When building, I knew exactly what I would do next with a table calc, but I thought this is where the LoD needed to be used, and despite my best efforts I just couldn’t figure it, but more on that later. For now, we’re going to use a table calculation to replicate the value across the whole ‘window’.

Avg of Selected Sub Cat

WINDOW_MAX([Selected Avg])

This is basically looking for the maximum value of the Selected Avg field, which is 152 (as all the other values are 0).

Add this to the view, and set the table calculation to compute using Sub-Category. This is just good practice when using table calcs, as it means wherever the pill gets moved to in the view, it will retain the same computation.

Variance

[Avg Qty]-[Avg of Selected Sub Cat]

Add this onto the table, and again set the table calculation to compute by Sub-Category.

If you change the value in the pSelectedSubCat parameter, you’ll see the last 3 columns change.

So now we’ve just got a few more fields to create that we’ll need on the viz.

We need to be able to identify the selected Sub-Category which will be used to colour the bars.

Is Selected Sub Cat?

[Sub-Category]=[pSelectedSubCat]

The tooltip also shows the text ‘more’ or ‘less’ when describing the display, so we need a field for this

TOOLTIP: more or less

IF [Variance] <= 0 THEN ‘less’ ELSE ‘more’ END

And finally, the tooltip displays the variance as an absolute number, so we need a field for this too

TOOLTIP:Variance

ABS([Variance])

So this is all the core fields you’ll need to build the solution, so if you’re not interested in the LoD route, skip over the next bit 🙂

The LoD Solution

After watching Tableau Tim’s video, I realised why I had struggled to get an LoD solution to work. I needed to revisit my approach to calculating the average quantity, a step I hadn’t originally considered.

Now in the interest of time, I’m not going to write out why the calculation below works in detail when Tim demonstrates it so eloquently in his video 🙂

Qty Inc Manufacturer

{INCLUDE [Manufacturer] : SUM([Quantity])}

This field is going to help us get our ‘average quantity’ value.

Add Sub-Category, Quantity and Qty Inc Manufacturer into a tabular view, and change the aggregation of the Qty Inc Manufacturer pill from SUM to AVG. Order by this field descending, and you can see we have the same values as the Avg Qty field I created in the above solution.

This time, I’m going to start with the field to identify the selected Sub Category.

Is Selected Sub Cat

[pSelectedSubCat]=[Sub-Category]

Then we need to identify the value associated to the selected sub category, and will do this with two fields

Selected Qty

IF [Is Selected SubCat] THEN [Quantity] END

Selected Qty Inc Manufacturer

{INCLUDE [Manufacturer] :SUM([Selected Qty])}

Add these onto the view, and you can see the behaviour. Note this time I chose not to bother with an ‘Else 0’ statement (it wasn’t necessary for the above either).

Now we want to be able to ‘spread’ this value across all rows, and the Comparative Sales Analysis example in this Tableau blog post helps here (and I’ve just seen that Tableau Tim has produced an EXCLUDE LoD video too, which I’m sure will explain things very well).

Overall Selected Qty Inc Manufacturer

{EXCLUDE [Sub-Category], [Is Selected SubCat]: AVG([Selected Qty Inc Manufacturer])}

Note – I found I needed to add the Is Selected SubCat dimension into the statement, to get the tooltips working on both the bar charts.

And once again, we can now compute the variance, and the variance required for the tooltip, and the more or less values:

Variance

AVG([Qty Inc Manufacturer]) – MIN([Overall Selected Qty Inc Manufacturer])

TOOLTIP:Variance

ABS([Variance])

TOOLTIP : more or less

IF [Variance] <= 0 THEN ‘less’ ELSE ‘more’ END

Building the Viz

To build the viz

  • Add Sub-Category to Rows
  • Add Avg Qty (or Qty Inc Manufacturer set to AVG) to Columns. Sort by the field descending.
  • Add Variance to Columns
  • On the Avg Qty marks card, add Is Selected Sub Cat to the Colour shelf and adjust accordingly
  • On the Variance marks card, add Variance to the Colour shelf, and notch down the transparency to about 75%
  • Add TOOLTIP:Variance and TOOLTIP:more or less to the Tooltip shelf of the All marks card
Then it’s just a case of formatting the display and the tooltips.

Remember – if you’re working with the table calc solution, make sure all the table calculation fields in the display (those with the triangle symbol) have all been set to compute by Sub-Category.

Adding the dashboard interactivity

When you click on a Sub-Category, the variance needs to change. This is managed via a Parameter Dashboard Action. Once the viz has been added to a dashboard then add a dashboard action that on select of the viz, sets the pSelectedSubCat parameter, with the value of the field from the Sub-Category dimension.

There’s also an additional feature in this dashboard that stops the selected field from being highlighted on click. To stop this from happening, create 2 new fields

True

True

False

False

Add both of these to the Detail shelf on the All marks card of the chart viz.

Then on the dashboard, add a dashboard filter action, which on select targets the chart sheet, and maps True to False. As this is never a match ie ‘true’, the filter doesn’t apply.

Hopefully I’ve covered everything. My published vizzes are here

Happy vizzin’! Stay Safe!

Donna

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