In Tableau, every data field can be classified as a Dimension or Measure.
Let me explain in detail!
When you connect to a data source, Tableau automatically classifies each field in the data source as a Dimension or Measure. You can find these in the data pane that is on the left-most side of the Tableau screen which is split into sections.
Dimensions on the top and Measures on the bottom are separated with a very light gray line. (See Fig 1)
Dimensions are commonly known as a field of categorical data. Dimensions hold discrete data such as Customer Names that cannot be aggregated. It also contains characteristic values such as Date and geographical data. In Fig 1, all the fields which are in blue are Dimensions.
A Measure is a field that can be aggregated. It is something that can be collected, counted, or combined in some way to return a single value. In Fig 1, all the fields which are in green color are Measures.
Let’s take an example with the Superstore dataset to explain more in detail:
Let’s drop Region on the Rows shelf and Sales on the columns shelf, we can see that the Dimension divides Region data into four different groups, and the Measure - Sales automatically displays the sum of sales in each different region.
If we have noticed, we have a blue pill for Region and a green pill for Sales
The Blue pill represents the item that is discrete, which means it will have separate distinguished parts and sections.
The Green pill represents the item that is continuous, which means it is aggregated.
Dimensions are always discrete, but not always. Measures are almost always continuous.
In Tableau, a Dimension can be converted to a Measure and vice versa. But there is a distinct difference between the two that will affect your visualization.
Let me explain this with an example:
Let’s convert the Dimension Product Name into Measure. To do this just right-click on the Product name and select the option “Convert to Measure”. We can see that the “Product Name” changed from Dimension in Fig 3 to a Measure “Product Name(Count)” in Fig 4.
Fig 3 Fig 4
Let’s drop the new “Product Name(count)” Measure into the Columns shelf and see the visualization.
We can see the new bar chart with a Distinct count of Product Names in different regions with a continuous axis as in Fig 5.
Now let’s look at a Dimension that can be Continuous.
Drop Order Date to the Columns shelf which has default discrete YEAR and discrete QUARTER. Right-click on the QUARTER(Order Date) and select the option” Quarter” from the bottom section(highlighted) which is Continuous and the top section are Discrete as in Fig 6
We can see from Fig 7 that the “QUARTER(Order Date)” Dimension field has changed to a Continuous field.
To conclude, it is very easy to get confused about dimensions and measures with discrete and continuous. Especially since all the dimension fields are blue and the measure fields are green when you first load in a dataset! Converting from measure to dimension and discrete to continuous can easily be done in Tableau but they will affect your visualizations. Converting may give you a better visualization than your initial one though so it is encouraged to try out which combination of these parameters yields the best results.
Hope this blog gives you a basic understanding of Dimensions vs Measures and Discrete vs Continuous.
Thank you for reading!!