Introduction to Tableau Calculations

Overview

• Target Audience: New to Tableau or need a refresher on calculations
• Covered Topics: What calculations are, where to find them, how to create them, types of calculations, examples

What Are Calculations?

• Extend your data source with logic, business rules, or existing data points
• Types of Calculations in Tableau:
  • Basic Calculations
  • Level of Detail (LOD) Expressions
  • Table Calculations
• Focus on Basic Calculations: Row Level Calculations and Aggregate Calculations

Components of Calculated Field

• Name
• Comments (optional)
• Field Names (drag from sidebar)
• String Literals (text embedded into calculation)
• Operators (e.g., string concatenation using “+”)
• Parameters
• Functions (built-in reusable code)

Creating Calculated Fields

1. Drop Down Menu
   • Under data source window
   • Opens calculated field editor
2. Right-Click on Field
   • Select “Create Calculated Field”
3. Menu: Analysis > Create Calculated Field
4. Ad Hoc Calculations
   • Double-click empty area in columns/rows/marks card
   • Less feature-rich (no function list)
   • Limited to the current worksheet

Basic Calculations: Row Level

• Row level calculation: Derives value for every row from the data source
• Examples:
  • Email Domain Extraction
    • Use split or custom split
  • Full Name Creation
    • Concatenate first name, last name with operators
  • Conditional String Functions
    • Use functions like contains, starts with, ends with
    • Example: Identify tracks by U2/Bono using “contains”
  • Profit Identification
    • Field showing if each line item is profitable (Profit > 0)
  • Date Compositions
    • Use MAKEDATE to combine year, month, day fields
    • Use DATEPARSE for unconventional date formats
  • Date Calculations
    • Use DATEDIF to calculate intervals (e.g., days since invoice)

Basic Calculations: Aggregate

• Aggregate functions: Generate one result for a group of records
• Examples:
  • Counting distinct values
  • Sum, average, minimum, maximum of field values
• Aggregation happens by default with measures grouped by dimensions
• Creating Aggregated Calculated Fields
  • Example: COUNTD(Customer ID)
  • Example: Profit ratio calculation as aggregate (SUM(profit) / SUM(sales))

Practical Tips and Warnings

• Ad Hoc Calculations: Limited feature set
• Date Functions Differences: E.g., DATEDIF syntax is different between Tableau and SQL Server
• Validation: Always double-check calculated field results
• Aggregating First for Ratios: Important to aggregate (e.g., sum) before dividing to avoid incorrect values
• Documentation: Add comments in calculated fields for clarity
• Syntax Errors: Use Tableau's error hints to fix issues

Conclusion

• Covered basics and practical examples of Tableau calculations
• Stay tuned for future videos on LOD expressions and table calculations.