Fundamental Fields in Tableau
Understanding Continuous and Discrete fields (i.e. fundamental fields in Tableau) helps you in grasping the fundamentals of Tableau. Furthermore, you can also apprehend plotting graphs better. This is especially useful for beginners. However, before diving into the details, you need to know what are Headers and Axes in Tableau.
Headers show the member names of each field on the shelves. The headers are present at the top of the viz, as shown below.
Axes show data points that lie within a range of values. Axes are present at the bottom of the viz, as shown below.
This should give you a clear understanding of Headers and Axes.
Continuous and Discrete
When you add a Continuous field into the Rows or Columns shelf, Tableau creates a Header. Similarly, when you add a Discrete field into the Rows or Columns shelf, Tableau creates an Axis. The easiest way to identify whether the viz is created with a Discrete or Continuous field is by checking the colour of the pill; green indicates Continuous, and blue indicates Discrete fields in Tableau.
To define in terms of Statistical data, Discrete values are distinct. Also, there are no intermediate values between any two Discrete values. However, Continuous values have infinite possible values in-between two values.
In Tableau, you can sort Discrete values, but not Continuous values. For example, the viz below shows the sorting of ‘Year’ in descending order on the basis of the sales.
This is due to the reason that the axis is continuous. As a result of the axis being Continuous, the Date always follows a chronological order.
If you want to include a discrete measure as part of a table calculation, uncheck ‘Ignore in Table Calculations’ (refer the image below)
Continuous data is usually useful for plotting the trend. If for some reason the line chart is broken, remove all the discrete fields from LOD (Level of Detail), and filter all the null values.
Assume a data-set with 5 years of data. A viz with date (Month) as a Discrete field and Sales, will by default sum up the sales for each month on every year so the viz will have 12 points (one for each month). On the other hand, a viz with date (Month) as a Continuous field will have 60 points (12 months for 5 years).
This example is shown below:
Knowing the restrictions in using Discrete, and Continuous fields provide a deeper understanding of the field. Below are few restrictions that need to be kept in mind while creating the Viz.
- Adding a reference line to a discrete field.
This feature is currently unavailable in Tableau Desktop, but there is a work around as shown here.
- Grand totals cannot be applied on Continuous Dimensions.
Most noteworthy, Discrete and Continuous fields are interchangeable. In other words, the user is able to convert a Measure Value, Date Dimension or any Numeric Dimension from discrete to continuous or vice-versa.
The above information on the working of the fundamental fields will help you be able to create a well-informed viz. Please subscribe for more information and as always you may look forward to more posts on Tableau from us.