Introduction
Calculated fields in Tableau allow you to create new data from existing data. This is essential for performing complex calculations, creating new metrics, and transforming data to meet your analysis needs. In this section, we will cover the basics of creating and using calculated fields in Tableau.
Key Concepts
- Calculated Fields: Custom fields created using existing data and functions.
- Functions: Predefined operations that can be used in calculated fields (e.g., mathematical, string, date functions).
- Syntax: The structure and rules for writing calculations in Tableau.
Creating a Calculated Field
Step-by-Step Guide
- Open Tableau and connect to your data source.
- Navigate to the Data Pane on the left side of the interface.
- Right-click on the Data Pane and select "Create Calculated Field...".
- Enter a Name for your calculated field.
- Write the Calculation using the calculation editor.
- Click OK to create the calculated field.
Example
Let's create a calculated field to calculate the profit ratio.
- Name: Profit Ratio
- Calculation:
[Profit] / [Sales]
Explanation
[Profit]
and[Sales]
are existing fields in your data source.- The calculation divides the profit by sales to get the profit ratio.
Common Functions
Mathematical Functions
- SUM(): Adds up all the values in a field.
SUM([Sales])
- AVG(): Calculates the average of the values in a field.
AVG([Sales])
String Functions
- LEFT(): Extracts a specified number of characters from the start of a string.
LEFT([Product Name], 3)
- CONCAT(): Combines two or more strings.
CONCAT([First Name], " ", [Last Name])
Date Functions
- DATEADD(): Adds a specified number of intervals to a date.
DATEADD('month', 1, [Order Date])
- DATEDIFF(): Calculates the difference between two dates.
DATEDIFF('day', [Order Date], [Ship Date])
Practical Example
Scenario
You want to create a calculated field to categorize sales performance as "High", "Medium", or "Low" based on the sales amount.
Steps
- Name: Sales Category
- Calculation:
IF [Sales] > 1000 THEN "High" ELSEIF [Sales] > 500 THEN "Medium" ELSE "Low" END
Explanation
- The
IF
statement checks the value of[Sales]
. - If sales are greater than 1000, it categorizes as "High".
- If sales are between 500 and 1000, it categorizes as "Medium".
- Otherwise, it categorizes as "Low".
Exercises
Exercise 1: Create a Discount Percentage Field
- Objective: Create a calculated field to find the discount percentage.
- Steps:
- Name: Discount Percentage
- Calculation:
[Discount] * 100
Exercise 2: Calculate Yearly Sales Growth
- Objective: Calculate the year-over-year sales growth.
- Steps:
- Name: Yearly Sales Growth
- Calculation:
(SUM([Sales]) - LOOKUP(SUM([Sales]), -1)) / LOOKUP(SUM([Sales]), -1)
Solutions
Solution 1: Discount Percentage
Solution 2: Yearly Sales Growth
Common Mistakes and Tips
- Syntax Errors: Ensure that your calculations follow the correct syntax. Tableau will highlight errors in the calculation editor.
- Data Type Mismatch: Make sure the fields you are using in calculations are of compatible data types.
- Using Functions Correctly: Familiarize yourself with Tableau's functions and their correct usage.
Conclusion
In this section, we covered the basics of creating and using calculated fields in Tableau. We explored common functions, practical examples, and exercises to reinforce the concepts. Calculated fields are powerful tools that can help you derive new insights from your data and perform complex analyses. In the next section, we will delve into creating dual-axis charts to enhance your visualizations.
Tableau Course
Module 1: Introduction to Tableau
- What is Tableau?
- Installing Tableau
- Tableau Interface Overview
- Connecting to Data Sources
- Basic Data Types and Structures
Module 2: Basic Visualization Techniques
- Creating Your First Visualization
- Using Marks and Cards
- Building Basic Charts
- Filtering Data
- Sorting and Grouping Data
Module 3: Intermediate Visualization Techniques
- Using Calculated Fields
- Creating Dual-Axis Charts
- Using Parameters
- Creating Maps
- Using Table Calculations
Module 4: Advanced Visualization Techniques
- Advanced Chart Types
- Using LOD Expressions
- Creating Dashboards
- Dashboard Actions
- Storytelling with Data
Module 5: Data Preparation and Transformation
Module 6: Advanced Analytics
Module 7: Performance Optimization
- Optimizing Workbook Performance
- Extracts vs Live Connections
- Reducing Load Times
- Performance Recording
- Best Practices for Performance
Module 8: Tableau Server and Online
- Introduction to Tableau Server
- Publishing Workbooks
- Managing Permissions
- Scheduling Extracts
- Collaborating with Tableau Online