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

  1. Calculated Fields: Custom fields created using existing data and functions.
  2. Functions: Predefined operations that can be used in calculated fields (e.g., mathematical, string, date functions).
  3. Syntax: The structure and rules for writing calculations in Tableau.

Creating a Calculated Field

Step-by-Step Guide

  1. Open Tableau and connect to your data source.
  2. Navigate to the Data Pane on the left side of the interface.
  3. Right-click on the Data Pane and select "Create Calculated Field...".
  4. Enter a Name for your calculated field.
  5. Write the Calculation using the calculation editor.
  6. Click OK to create the calculated field.

Example

Let's create a calculated field to calculate the profit ratio.

  1. Name: Profit Ratio
  2. 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

  1. Name: Sales Category
  2. 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

  1. Objective: Create a calculated field to find the discount percentage.
  2. Steps:
    • Name: Discount Percentage
    • Calculation:
      [Discount] * 100
      

Exercise 2: Calculate Yearly Sales Growth

  1. Objective: Calculate the year-over-year sales growth.
  2. Steps:
    • Name: Yearly Sales Growth
    • Calculation:
      (SUM([Sales]) - LOOKUP(SUM([Sales]), -1)) / LOOKUP(SUM([Sales]), -1)
      

Solutions

Solution 1: Discount Percentage

[Discount] * 100

Solution 2: Yearly Sales Growth

(SUM([Sales]) - LOOKUP(SUM([Sales]), -1)) / LOOKUP(SUM([Sales]), -1)

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.

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