How to Comment in Tableau Calculated Field

Writing a calculation in Tableau feels great, but coming back to it six months later to figure out what you did can feel like deciphering ancient hieroglyphs. This is where comments come in. This article will show you exactly how to add comments to your Tableau calculated fields to save your future self (and your teammates) a lot of headaches.

Why Bother with Comments in Your Calculations?

You might think your formulas are simple enough, but commenting is a small habit that pays off big time. It’s like leaving a helpful user manual right inside your workbook.

• For Your Future Self: You will forget the specific business logic or the reason for a particular tweak in a complex formula. A quick comment explaining the "why" behind your calculation can save you hours of reverse-engineering your own work.
• For Your Teammates: Collaboration is essential. When a coworker takes over your dashboard, comments help them get up to speed quickly and confidently. They can understand the purpose of a field without having to track you down for a 20-minute explanation.
• For Debugging: Is a calculation error breaking your beautiful dashboard? You can use comments to temporarily "turn off" parts of your formula. This helps you isolate the problem area without deleting your code.
• For Documentation: Comments serve as built-in documentation. Anyone opening the calculated field instantly gets context on what it does, who created it, and why it exists. This transparency builds trust in the data and the reports you build.

Think of it this way: the time it takes to write a thoughtful comment is minuscule compared to the time you'll waste trying to understand that same calculation a few months from now.

The Two Types of Comments in Tableau

Tableau offers two simple ways to add comments to your calculated fields, each suited for different situations. Learning both will give you the flexibility to document your work clearly and efficiently.

1. Single-Line Comments: These start with // and are perfect for short notes on a single line of code.
2. Multi-Line Comments: These start with /* and end with */. They are ideal for longer explanations, providing detailed context, or temporarily disabling a large block of code.

Let's break down how to use both, with examples you can apply right away.

How to Add Single-Line Comments (//)

Single-line comments are your go-to for quick, contextual notes. Anything after the // on that line will be ignored by Tableau's calculation engine.

Step-by-Step Instructions

1. Open the Calculated Field editor in Tableau by right-clicking in the Data pane and selecting "Create Calculated Field."
2. Write your formula or find the line you want to add a note to.
3. Type // either at the start of a new line or at the end of a line of code.
4. Type your descriptive comment after the slashes.

The text will turn gray, indicating that Tableau recognizes it as a comment and not as part of the formula.

Practical Examples of Single-Line Comments

Let’s say you are building a dashboard for an e-commerce store and need to create a few calculated fields.

Example 1: Basic Profit Ratio

A simple note explaining the purpose of the field is a great start.

// Calculates the overall profit ratio for all products
SUM([Profit]) / SUM([Sales])

Example 2: In-Line Comment for a Specific Adjustment

Sometimes you need to explain just one part of a multi-part calculation. An in-line comment is perfect for this.

// We subtract shipping cost here because it is not considered revenue
(SUM([Sales]) - SUM([Shipping Cost])) / COUNTD([Order ID]) 

Example 3: Explaining A Business-Specific Rule

Your business logic might not be obvious to everyone. Comments clarify these special cases.

// Adding a 15% uplift for the West realignment strategy
IF [Region] = "West" THEN [Sales] * 1.15 // Adding a 15% uplift for the West realignment strategy
ELSE [Sales]
END

How to Add Multi-Line Comments (/.../)

When a short note just won't cut it, multi-line comments give you the space you need. These are perfect for writing detailed headers for complex calculations or for temporarily "commenting out" large sections of code while you test something new.

Step-by-Step Instructions

1. Open the Calculated Field editor.
2. Find the part of your calculation that needs a detailed explanation or that you want to disable.
3. Type /* at the beginning of the comment block.
4. Press Enter and write your notes. You can use as many lines as you need.
5. Finally, close the comment block by typing */ at the end.

Everything between these two symbols will turn gray, signaling that it is a comment.

Practical Examples of Multi-Line Comments

Let's see how multi-line comments can bring an extra layer of clarity to your work.

Example 1: Creating a Calculation Header

This is a fantastic habit for critical fields used across many dashboards. It provides an immediate overview of the calculation's history and purpose.

/* 
Field: Adjusted MQL Score
Author: Jane Doe
Date Created: 2024-03-15
Last Modified: 2024-05-20 - Added logic for webinar attendance.

Purpose: This calculation assigns a score to Marketing Qualified Leads (MQLs) based on 
their engagement. The scoring model was updated last quarter to give more weight to 
high-intent actions like demo requests.
*/

CASE [Lead Source]
    WHEN "Webinar" THEN [Form Score] + 50
    WHEN "Demo Request" THEN [Form Score] + 100
    ELSE [Form Score]
END

Example 2: Commenting Out Code for Debugging

Imagine your calculation isn't working, and you suspect one part is the issue. Instead of deleting it, just comment it out to test your theory.

// Disabling this part to test the old logic
/*
IF [Region] = "International" THEN
    SUM([Sales]) * 0.90
ELSE
    SUM([Sales])
END
*/
 
// Reverting to the simpler calculation until the regional logic is fixed
SUM([Sales])

In this example, you can safely test the simpler SUM([Sales]) logic without losing the complex regional discount code that you need to fix later.

Best Practices for Writing Helpful Comments

Now that you know the syntax, how do you write comments that are genuinely useful?

• Explain the "Why," Not Just the "What." Your code already states what it's doing (e.g., SUM([Sales]) - SUM([Cost])). A good comment explains why. For example: // Using gross profit to align with the finance team's reporting standards.
• Be Clear and Concise. Avoid jargon and abbreviations unless they are standard at your company. Write for a new team member who has no context. A clear comment saves a future question.
• Add a Header to Complex Calculations. For any calculation with tricky logic that took you a while to figure out, a header with the author, date, and purpose is a professional touch.
• Don’t Overcomment. Adding // Sums up sales next to SUM([Sales]) doesn't add any value. Comment on the non-obvious parts: the complex business rules, the data quirks you're working around, or the reasons behind a specific constant.
• Update Comments When You Update Code. An out-of-date comment is worse than no comment at all. If you change the logic in a calculation, remember to update the corresponding comment so it doesn’t mislead the next person.

Final Thoughts

Mastering the simple art of commenting in Tableau using single-line // and multi-line /* .. */ syntax is a force multiplier for your analytics work. This habit makes your workbooks more professional, easier to debug, and far more collaborative, ensuring your valuable data work can be understood and built upon long into the future.

We know that a lot of data analysis still feels manual and overly complicated. This is why we created Graphed, to remove the friction between questions and answers. Instead of writing formulas and remembering syntax, you can connect your data sources - like Google Analytics, Salesforce, and Shopify - and create stunning, real-time dashboards just by describing what you want to see in plain English. This gets you straight to the insights, so you can focus on making decisions, not on becoming a BI expert.