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:
- The Data – simple data for the Seven Dwarfs.
- Connected to Dwarves.csv – Tableau connected to the data.
- Correct Number Displays – with one Measure in a table, Tableau uses the right format.
- Unwanted Format Changes – adding a second Measure causes Tableau to change the format.
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.
ConsequencesUser 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.