Dr Data Insight - M4: Calculated Fields & Data Blending

Welcome

M1: Getting Started Tableau

M2: Filters, Parameters and Drill Down

M3: Visual Best Practice and NHS Dashboards

M4: Calculated Fields & Data Blending

M5: Presenting Dashboards & Interview Delivery

Module 4: Calculated Fields & Data Blending

In this module, you’ll learn how to extend your Tableau analysis using calculated fields and data blending—two powerful features that enable you to go beyond basic visualisation and generate deeper, more meaningful insights. Calculated fields allow you to create custom metrics, flags, and logic directly within Tableau—for example, highlighting patients breaching waiting time thresholds or calculating bed occupancy rates. Data blending enables you to combine data from multiple sources, such as outpatient activity from one system and demographic data from another, even when a full join isn’t possible. As NHS analysts often work with disconnected or siloed datasets, these tools are essential for producing unified views of performance and patient care. By the end of this module, you’ll be able to build richer dashboards that reflect the complexity of real-world healthcare data.

Module 4: Calculated Fields & Data Blending - 4.1

Adding Analytical Power to Your Dashboards

So far, you’ve learned how to create compelling, interactive visualizations. But what if your data doesn’t tell the whole story—yet? That’s where calculated fields and data blending come in. This module teaches you how to build your own metrics, logic, and relationships, so Tableau can analyze your data the way your business actually works.

Learning Objectives

By the end of this module, you will be able to:

Create calculated fields using built-in Tableau functions
Apply string, date, number, and logical expressions
Use table calculations for ranked, percent, and moving average metrics
Understand and apply Level of Detail (LOD) expressions
Combine data from multiple sources using joins and blending
Troubleshoot common data relationship challenges

Lesson Breakdown

4.1 Introduction to Calculated Fields

What is a calculated field?
When to create your own metrics or logic
Creating basic calculations: profit margin, sales per customer
Overview of calculated field editor
Hands-on: Build a “Profit Ratio” field from Sales and Profit

4.2 Common Functions in Tableau

String functions: LEFT, RIGHT, LEN, FIND, CONCAT
Date functions: TODAY, DATEDIFF, DATEPART
Numerical functions: ROUND, CEILING, ZN, ABS
Logical functions: IF/THEN, CASE, ISNULL
Hands-on: Clean messy data fields with string and date calculations

“Data preparation inside Tableau reduces your reliance on upstream fixes.”

4.3 Table Calculations

What are table calculations? How do they differ from calculated fields?
Common uses: Running totals, percent of total, moving averages
Understanding Compute Using and Table (Down) logic
Hands-on: Build a chart showing YOY growth using table calculations

4.4 Level of Detail (LOD) Expressions

FIXED, INCLUDE, and EXCLUDE explained
When to use LOD vs table calculations
Creating complex aggregations across different levels of granularity
Hands-on: Build a view showing each customer’s average order value, regardless of filter

"LOD expressions let you write business rules the way your CEO thinks—not the way your table is structured."

4.5 Data Blending and Relationships

Tableau’s two-layer model: logical vs physical layer
Joins: inner, left, right, full outer
Data blending vs relationships – what’s changed in recent Tableau versions
Primary vs secondary data sources
Hands-on: Blend Excel sales data with SQL customer data to build a full performance view

4.6 Troubleshooting Calculations and Data Blending

Common errors: null values, aggregation mismatches, level of detail conflicts
Debugging tools: describe sheet, calculation audit, performance recorder
Best practices for documentation and calculation naming

Module 4: Calculated Fields & Data Blending - 4.2

🧠 Knowledge Check

Scenario-based quiz: Which type of calculation should you use?
Hands-on challenge: Create a dashboard that uses one calculated field, one table calc, and one blended data source
Discussion prompt: “What calculations or blended views would add value in your current role or organization?”

📌 Key Takeaways

Calculated fields give you the flexibility to derive new insights from raw data
Table calculations allow you to analyze trends across the structure of your view
LOD expressions help you summarize data at different levels, regardless of filters
Blending and joining data sources let you see the whole picture—even when your data lives in silos

🎓 What’s Next?

In Module 5, we’ll bring everything together to focus on Presentation, Dashboard Design, and Real-World Interview Scenarios. You’ll learn how to turn your Tableau work into executive-ready dashboards and confidently tackle real analytics tasks.

Calculated Fields & Data Blending Quiz

Disclaimer: The videos included have been thoughtfully selected to support and enrich the learning experience. While not essential to the completion of the course, they offer valuable insights that may deepen your understanding of the module content. Dr Data Insights does not claim authorship or involvement in the creation of these tutorials.