Double Marginal Histogram

Weeks ago I published what I call a Double Marginal Histogram chart. Double because it combines 2 highlight tables with 3 marginal histograms on their sides. Here is how it looks like using Tableau’s Sample Superstore dataset (click to open on Tableau Public):

Marginal Histogram (QuarterMonthWeek)

Note: On my original business case I had the first highlight table / histogram by month and the second set by hour. As Sample Superstore does not have data on hour level I had to adapt this here.

Why did I design this? I wanted to be able to quickly detect within each combination of month (or quarter) and weekday when was the best hour to promote certain products. And I think this chart was able to give me just that.

On the adapter example I can quickly find that technology sales are horrible on Wednesdays in California (come on 0 sales on January and October on Wednesdays? Really?). On the opposite side I can also see that Fridays are great for almost every quarter, in special December (Xmas time right?). Thanksgiving and Xmas shopping make a clear impact on Q4 as well.

Another reason that I designed this is because is really super easy to do. It took me less than an hour from the original draft to the final design, including the highlight actions.

So how should you start?

  1. Start with the highlight tables. Drag the two discrete time dimensions (blue pills) to rows and tables and the measure to color.


2. Format your table (grid lines, fonts, colors, etc) because after that you will do a lot of duplications.

3. Duplicate the sheet to create the 2nd highlight table. Keep the Rows as is and just replace the Columns with a more granular date dimension (month or hour for example).


4. Now we need to create 3 marginal histograms (which are very simple bar charts).  Start with the ones that are on top of each table. In the example, Quarterly and Monthly. You can again duplicate the sheet and drag the Measure to the Rows shelf:


5. Some little formatting here and you are good to duplicate it again and replace the Date dimension again.

6. The same process can be done with the Weekday histogram. Duplicate the highlight table and now instead of moving the Measure to Rows, do it to Columns.

7 Now you have all charts you need so it is time to lay down them on Dashboard. I am #teamFloat but on this case I used layout containers as I understand this is the most used option in Tableau. Layout containers can be tricky so if you can’t align all elements precisely, I recommend moving all objects to float to have full control on sizes and position.

You may end up with a Dashboard like this one:

Marginal Histogram (blank space).png

So I asked myself… what the hell do I do with that empty space on top right. That is maybe the most important area of the dashboard (in usability studies and eye tracking too) and I could not leave it empty. So I decided to put there the key BANs for the report, the total of sales, the % of sales against total, the % of sales for the product in the State and, as this is all about showing time, added the respective timelines there to show the trend overtime. Oh, I also used the BANs as color legend for the timeline.

I hope you can all take advantage of this tool and, who knows, bring more ideas to convey even more data in such a short space.


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