Sunday, May 13, 2012

Unexpected Number Reformatting

Tableau sometimes decides that it will format numbers in ways that don't seem to make much sense. In some cases it even contradicts itself, changing a measure's number format in mid-visualization.

The Tableau Published Workbook below demonstrates one such scenario. To see it, cycle through the dashboards in sequence:

  1. The Data – simple data for the Seven Dwarfs.
  2. Connected to Dwarves.csv – Tableau connected to the data.
  3. Correct Number Displays – with one Measure in a table, Tableau uses the right format.
  4. Unwanted Format Changes – adding a second Measure causes Tableau to change the format.
Additional content follows the Workbook.

The Video

This video shows the reformatting in action. The Dwarves data is in the Tableau Public workbook, which can be downloaded.

The primary problem

When someone loads some data there's usually an expectation about the data's nature. In the Dwarves data, the number of Gems mined is a whole number-an integer, and the number of years working in the mine is known to be the number of whole years-another integer.

When Tableau places the Gems and Years in Mine values into an empty table it uses an integer format - no decimal digits. However, upon placing a second value into the same table Tableau decides that it's now appropriate to use a decimal format with two decimal digits.

This is bad.


User confusion — changing a visible attribute on a significant element causes the user cognitive problems.

Unrecoverability — once this happens it's unclear how to correct the situation, or prevent it from happening in the future.


  1. What you are leaving out, is that you changed from a normal continuous aggregate pill on the Text shelf to the Measure Values pill on the Text shelf.

    These pill arrangements have different default logic, as you can see.

    So I hear you asking for the default logic to be consistent instead of jarring different. They got it right with one, but wrong with another.

  2. But I didn't do anything with any pills. I only drop measures into the worksheet. Tableau handles the pill placement and configuration, and in doing so applies an inappropriate number format to the fields I'm interested in.

    I can see where this behavior seems reasonable from the perspective of whomever was tasked with programming it, but it's certainly not reasonable from the person who's simply trying to use Tableau to make sense of their data.

    Tableau should always -always- respect the most appropriate presentation for the data it's showing. When the data coming in is integers, Tableau should not apply a decimal digit format to simple aggregations, and it's debatable whether doing so with ratios is a good or bad idea.