Understanding Tableau Concepts: Additional topics on Dimensions and Measures in Tableau
This is the fourth article in Tableau Desktop Specialist Exam Topic Series List.
Although we have covered most of the topics regarding Dimensions and Measures in Tableau there are few additional topics left.
What are Tableau generated fields?
After we connect to any data source using Tableau the Data pane will contain an additional number of fields that were not present in the original data. These are the Tableau-Generated fields as they are automatically created by Tableau.
Given below are the Tableau-Generated Fields:
1. Measure Names
2. Latitude (generated)
3. Longitude (generated)
4. NameofTable(Count)/ Number of Records
5. Measure Values
The below image provides a visual summary of the Tableau Generated Fields present in the Data Pane in Tableau Desktop
NOTE: The fields names for Tableau-generated field are are Italicized (Italic font)
NOTE: This example displays the Data pane for a Data Model with a single Table
Given below is the detailed explanation for each of the Tableau-Generated Fields:
Measure Names:
The Measure Names field contains the names of all measures in the data, combined into a single field with discrete values.
We need to use it along with Measure Values to blend measures.
Latitude and Longitude:
When Tableau interprets fields to be geographic fields that can be used with maps, it automatically geocodes the data and includes Latitude (generated) and Longitude (generated) fields.
We can use these fields to overlay the data on live maps.
Count of Table/ Number of Records:
Starting with Tableau 2020.2, every table in a data source has a Count field, in the form of NameofTable(Count).
The table count field is an automatically generated, calculated field.
COUNT of table = SUM of the number of records per table
We can’t build calculations on top of a table’s Count field, and it is aggregate-only.
In versions of Tableau before 2020.2, the Number of Records field is an automatically generated, calculated field that is set to the number 1.
Measure Values:
The Measure Values field contains all the measures in the data, combined into a single field with continuous values.
We need to use it along with Measure Names to blend measures.
Among the Tableau-Generated Fields only Measure Names is a Dimension while the others are Measures.
Hence the split is 1 Dimension and 4 Measures.
How are the Dimensions and Measures displayed in the Data pane for a Data Model that contains two tables?
By default in the Data pane, dimensions are displayed above the gray line, and measures below the gray line.
Consider that we are having two tables in a Tableau Data Model.
Even for this scenario within each Table the dimensions are displayed above the gray line, and measures below the gray line.
The below image provides a visual summary of the Dimensions and Measures in the Data pane for a Data Model with two tables
Where are fields that do not belong to a specific table displayed in the Data pane?
Fields that don’t belong to a specific table are displayed in the general area below the tables.
Typical examples of such fields are aggregated calculations, calculations that use fields from multiple tables, Measure Names, and Measure Values.
Here Profit Ratio is an aggregated calculation that is displayed in the general area below the tables.
Behavior of using a Dimension versus Measure in the Filters shelf
When we drop a discrete dimension on the Filters shelf, we get a Filter dialog box that prompts us to choose which members of the discrete field to include or exclude in the view.
When we drop a continuous measure on the Filters shelf, we get a Filter dialog box that prompts us to choose an aggregation for the filter
In case we select All values we will get another Filter dialog box that prompts us to specify how to filter the continuous range of values
i.e. Range of values, At least, At most and Special.
Behavior of using a Dimension versus Measure on Color in the Marks card
When we drop a discrete dimension on Color in the Marks card, Tableau displays a categorical palette and assigns a color to each member of the field.
When we drop a continuous measure field on Color in the Marks card, Tableau displays a quantitative legend with a continuous range of colors.
When there are both negative and positive values for the continuous measure field, the default range of values will use two color ranges and the Edit Colors dialog box for the field has a square color box on either end of the range. This is known as a diverging palette.
Easy process to determine if a field is a Dimension or a Measure in Tableau
The first question we need to ask is “Is the Data Type of the field = Number?”
If the answer for this question is No then the field is a Dimension.
If the answer for this question is Yes then we need to proceed to the next question.
The second question we need to ask is “Does it make sense to aggregate the field ?”
If the answer for this question is No then the field is a Dimension.
If the answer for this question is Yes then the field is a Measure.
The below flow chart gives a visual summary of this process
The conclusion from this process is that all Non-numeric fields are Dimensions but not all Numeric fields are Measures.
What are the key topics for the TDS exam?
As per the TDS exam rules I cannot mention the actual questions of the exam but I can suggest certain key topics (in no specific order) based on which questions may appear with respect to the additional topics on Dimensions and Measures concept.
- What is the basic difference between Measure Names and Measure Values?
- What is the typical behavior of dropping a Dimension/ Measure in a specific part of a view? e.g: Rows shelf, Columns shelf, Filters shelf or Color in the Marks card
- How are the Latitude and Longitude fields used in Tableau?
- How do dimensions and measures differ in Tableau? Choose Two
I hope this article is useful for all Tableau users especially for anyone just starting their Tableau journey and who want to prepare for their Tableau Desktop Specialist Exam!!!
REFERENCES:
For the topic Easy process to determine if a field is a Dimension or a Measure in Tableau:
Tableau Dimensions and Measures EXPLAINED | #Tableau Course #46 by Baraa Khatib Salkini
