# Can you visualise percent difference from a selected date?

Lorna Brown returned this week with her first challenge of 2022 which was aimed at practising tableau calculations, although when I completed the build, I realised I actually didn’t use any – oops! I’d ended up using an LoD based solution instead. As is often the case in Tableau, there can be multiple ways to solve a problem, so I created another solution involving table calcs. As I blog I will endeavour to provide both sets of calculations used and make it obvious when I do so. Hopefully, it’ll all make sense 🙂

Building the calculated fields

After connecting to the data, the first step I did was to create a parameter to store the ‘selected date’. I hard coded/defaulted this to 1st Nov 2020.

pSelectedDate

Date parameter defaulted to 01 Nov 2020

Show this on the worksheet, so you can test what happens when you manually change it later.

As I typically do, I’m going to work in a tabular format to sense check all the calculations we’re going to need before I start visualising the information graphically.

To start add Company then Date (set to exact date & discrete) to Rows then add Close to Text and change the aggregation to AVG.

I now want to work out what the value of the average Close is on the selected date (in this case 01 Nov 2020) for each company, and I want this value to be displayed against every row associated to that company.

Close on Selected Date per Company

LOD Option

{FIXED [Company]: AVG(IF [pSelectedDate]=DATETRUNC(‘month’,[Date]) THEN [Close] END)}

Table Calc Option

WINDOW_MAX(AVG(IF [pSelectedDate]=DATETRUNC(‘month’,[Date]) THEN [Close] END))

Drag this field onto the table. If you’re using the LoD option, change the aggregation to AVG (although as we’re working with the data at the lowest granularity, SUM gives the same value, it just makes ‘more sense’ to me). If you’re using the Table Calc option, change the table calculation so that it is computing by Date only. In the below screen shot, I have included both versions of the calculation which match each other. Scrolling down, you should be able to verify that the value displayed in the new field(s) for all rows for a specific company, matches the value in the first column for the selected date. Test by entering different dates in the parameter (though make sure you’re just entering 1st of month each time, as that is what our Date field contains).

Now that for each row we have an average Close value and the average Close value on a specific date, we can work out the percentage difference for each row.

% Diff from Selected Date

LOD option

(AVG([Close])-AVG([Close on Selected Date per Company]))/AVG([Close on Selected Date per Company])

Table Calc option

(AVG([Close])-[Close on Selected Date per Company])/[Close on Selected Date per Company]

There is a slight difference in the syntax as the table calc option is referring to a field that is a table calculation and which is already aggregated, so there’s no need to aggregate again (ie wrap in an AVG…. Tableau will error if you try to do this).

Format this to a Percentage with 0 dp.

Once again I am choosing to show both versions on the screenshot below. Again if you’re using the table calc version, you need to verify the calculation is set to compute by Date only.

So now we have the core fields we need to start building the viz.

I am now just going to refer to the calculated field names I’ve mentioned above and not differentiate between LoD or table calc version. The only thing to remember is when adding the table calc fields, set the compute by, and if you’re using the LoDs, set the aggregation to AVG (although SUM will work too due to the level of aggregation we’re at).

Building the viz

On a new sheet add Date to Columns and set to the continuous Month level or exact date (either will work in this instance, since we only have 1 date per month in the data set). Add % Diff from Selected Date to Rows. Add Company to Colour and adjust to suit (use the hue circle colour palette).

Add Company to the Label shelf and also add % Diff from Selected Date to the Label shelf.

Adjust the Label settings, so the labels only display at the end of the line.

To make the text match the mark colour, click Label >then expand the Font dialog by clicking the arrow to the right, and select Match Mark Colour.

To format the % value displayed, right-click on the % Diff from Selected Date pill on the Text shelf, and select format. In the formatting pane that appears on the left hand side, change the number formatting to custom ▲0.0%;▼0.0% ( I use this site to get the shapes I need – just copy and paste)

Now rearrange the text on the label so that company is displayed first.

To format the Date field within the tooltip and the axis, right click on the Date pill in Columns and select format. On the Format Date pane on the left hand side, set the Dates value on the Pane tab, in the Default section, to custom : mmm yy. Then click on the Axis tab and set the Dates value in the Scale section to the same custom mmm yy value.

The Tooltip

We need quite a few fields on the Tooltip to get the information required.

Add Close and Close on Selected Date per Company to Tooltip. We also need a couple more calculated fields

TOOLTIP – Selected Date

[pSelectedDate]

format this field to custom mmm yy

TOOLTIP – % Diff

[% Diff from Selected Date]

Format this to % with 0 dp.

Add both these to the Tooltip too, then adjust the wording on the tooltip as required.

The Reference Line

Add pSelectedDate to the Detail shelf. Then right click the date axis and Add Reference Line. Adjust the settings so there is a Line for the Entire Table, which references the pSelectedDate value and has a custom Label of Reference Date: <Value>. Set the tooltip to None and the Line to be dotted

Format the pSelectedDate value displayed, by right clicking on the pill on the Detail shelf and set the Dates format on the Pane tab to mmm yy.

The right click on the Reference Date: Nov 20 label itself and select Format, and change the alignment to the top.

Finally, remove the axes titles, remove the gridlines and all axes rulers and change the worksheet background colour. Again, format the reference line label, so there is 0 transparency.

Test the visualisation by manually changing the date of the parameter to the 1st of another month and seeing how the viz updates.

Building the interactivity

Add the sheet to a dashboard, then create a parameter action, the runs on select of a mark on your sheet. It should change (target) the pSelectedDate parameter passing in the Date field

The only problem with this, is that when selecting a mark, the line relating to the mark is highlighted while the others ‘fade’ into the background. To prevent this from happening :

• Create a new calculated field called True which contains the value True
• Create a new calculated field called False which contains the value False
• Add both these fields to the Detail shelf on the line chart.
• Add a Dashboard Filter action, which runs on select, and has the sheet on the dashboard as it’s source, and the sheet in the workbook as it’s target. Set to show all values when selection is cleared, and filter by selected fields, setting True = False.

My published vizzes are here

Happy vizzin’! Stay Safe!

Donna