By: Eric Parker
Eric Parker lives in Seattle and has been teaching Tableau and Alteryx since 2014. He's helped thousands of students solve their most pressing problems. If you have a question, feel free to reach out to him directly via email.
One of Tableau’s greatest strengths is the ability to easily and intuitively visualize historic information. When that data is broken out by date, Tableau can display the data broken out by “Date Part” or “Date Value”. This terminology and concept is unique to Tableau and provides the designer with a lot of flexibility.
It’s easy to misunderstand the differences between these two date visualization methods. Let’s walk through what makes them unique and which scenarios each is best for.
Date Parts
If you left-click and drag a date field into a worksheet the pill will default to Date Part Year. You can see in the worksheet below that the default pill color is blue indicating it is Date Part, not Date Value. When a date field is visualized as Date Part it creates labels (notice 2019 is selectable) instead of a continuous axis.
One of the most distinctive features of Date Parts is that data is aggregated at the selected date unit level. For instance, in my example data set there are thousands of rows of transactions spanning four years, but when I select Date Part Month there are only 12 data points visualized.
In this case, all January sales (regardless of year) are aggregated and consolidated into a single point.
You can choose between different date units by selecting the drop down on a date field pill and selecting the desired date unit.
On the dropdown:
In action:
Date Parts are primarily used in two instances.
Comparative/Overlay Analyses:
Text Tables:
You can also use the drop-down on a date unit pill to select a Date Value. Date Values are on the bottom of the selection dialogue whereas Date Parts are on the top.
Date Values
Date values are primarily used to display chronological progress. They create a continuous axis broken down at the date unit selected. Date Values are green pills by default.
On top of being used to display chronological progress, Date Values are often paired with Forecasts and Trends.
Forecasts:
Trends:
History of Date Types in Tableau
Historically Date Parts were referred to as “Discrete Dates” and Date Values were referred to as “Continuous Dates”. In old Tableau documentation you may still see those terms used. They decided those terms were too confusing and started phasing them out a couple years ago.
To keep it simple, when you hear the terms “Discrete” in Tableau think of “Creates Labels”. When you hear the term “Continuous” think “Creates Axes”.
Technically, you can make Date Values discrete and you can make Date Parts continuous. For instance, observe this graph displaying Sales by Date Value Month.
If I select the drop-down and switch the pill from Continuous to Discrete…
...the axis changes into labels.
Switching a date pill from Continuous to Discrete or vice versa should only be used in rare circumstances. The majority of the time, that will not be necessary.
This graphic displayed earlier should summarizes the details of the blog post in a succinct fashion.
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