What is Proportional Brushing in Tableau?

A standard interactive dashboard lets you click on a data point to filter or highlight other charts, but this often erases the broader context. Proportional brushing is an advanced Tableau technique that solves this by showing you both a selected segment and its relationship to the total, all in one view. In this guide, we'll walk through what proportional brushing is, why it's so effective for data storytelling, and the exact steps to build it in your own Tableau dashboards.

What Exactly Is Proportional Brushing?

Proportional brushing is a data visualization technique that allows a user interaction (like a click) on one chart to show a part-to-whole relationship in a second chart. Instead of just filtering the second chart to the selected data, it shades or layers the selected portion on top of the total amount. This lets your audience instantly grasp the significance of the part they selected relative to the whole.

Let's compare it to Tableau's default actions to see why this is so different and powerful.

• Standard Highlighting: Imagine you have a map of the United States and a bar chart of total company sales. If you click on the "West" region on the map, a standard highlight action would fade out all non-West sales in the bar chart. You can still see the shape of the total, but it's hard to compare the dim bars to the highlighted one. The context is there, but faded.
• Standard Filtering: Using the same setup, a filter action would completely remove all non-West sales from the bar chart. All you would see is the sales for the West region. This completely removes the context. Is the West region's performance great? Is it small? You have no idea because the frame of reference (the total) is gone.
• Proportional Brushing: With proportional brushing, clicking "West" would keep the bar chart of total sales visible in a neutral color (like light gray) and then layer the sales data for the West region over it in a bright, contrasting color. The viewer immediately sees two things: the absolute sales value for the West, and how much of the total sales it represents. The context is not just preserved, it's the main focus.

Why Use Proportional Brushing? The Value of Context

The primary benefit of proportional brushing is its ability to maintain context. Often, an isolated number is meaningless without something to compare it to. Knowing that a marketing campaign generated $50,000 in revenue sounds good, but what if total revenue was $5 million? Suddenly, that $50k looks tiny. Proportional brushing bakes this comparison directly into your dashboard interactions.

Here’s why that matters:

• It tells a richer data story. It guides the user's attention to a specific segment while constantly reminding them of its relative importance. This helps answer not just "what is this value?" but also "how much does this value matter?"
• It aids clearer decision-making. When analyzing performance, seeing a segment's contribution to the whole can help prioritize efforts. A product category that makes up 40% of total profit deserves more attention than one that makes up only 1%. Proportional brushing makes these disparities visually obvious.
• It encourages deeper data exploration. An intuitive, responsive dashboard invites users to click around and ask more questions. They can quickly investigate different regions, product lines, or marketing channels and have an “a-ha!” moment when they see a small segment's surprising impact, or a large segment's underperformance.

How to Implement Proportional Brushing in Tableau: A Step-by-Step Guide

Let's build a dashboard with proportional brushing using Tableau's sample Superstore dataset. Our goal is to create a dashboard where clicking on a segment in a pie chart showing sales by Region will proportionally color a bar chart showing sales by Sub-Category.

This technique relies on three key Tableau features: Sets, Calculated Fields, and Dashboard Actions.

Step 1: Build Your Base Worksheets

First, we need to build the two charts that will live on our dashboard: the "source" chart that we'll click on, and the "target" chart that will display the proportional brush effect.

Create the Source Sheet: Sales by Region Pie Chart

1. Open a new worksheet and call it "Sales by Region Pie".
2. From the Data pane, drag the Region dimension to the Color card.
3. Drag the Sales measure to the Angle card.
4. Change the chart type in the Marks card dropdown to Pie.
5. Drag Sales and Region to the Label card to see the values on the chart. Your pie chart is ready.

Create the Target Sheet: Sales By Sub-Category Bar Chart

1. Create a second worksheet and name it "Proportional Sales by Sub-Category."
2. This is where we’ll set up the layering effect. Before we create the chart, we need to create a Set and a Calculated Field.

Step 2: Create a Set for Interaction

A Set in Tableau is a custom field that defines a subset of your data. We'll create one based on the Region field. Our dashboard action will later add and remove regions from this set based on what the user clicks.

1. In the Data pane, find the Region dimension, right-click it, and select Create > Set.
2. Name the set "Region Set."
3. Don't select any regions in the list, just leave it empty for now and click OK.

Step 3: Create the Calculated Fields for Layering

This is where the magic happens. We'll use this set to create two calculated fields. One will only contain sales data for the region(s) selected (i.e., in our set), and the other will hold the total sales.

Calculated Field 1: Selected Sales

1. Go to Analysis > Create Calculated Field.
2. Name the field "Sales (Selected Region)."
3. Enter the following formula:

IF [Region Set] THEN [Sales] END

This formula tells Tableau: "If a record's region is in our Region Set, then return its sales value. Otherwise, return nothing (NULL)."

1. Click OK.

Now we have all the pieces to build our target bar chart.

Step 4: Build the Dual-Axis Proportional Bar Chart

We'll use a dual-axis chart to layer our "Selected Sales" on top of the "Total Sales."

1. On your "Proportional Sales by Sub-Category" sheet, drag Sub-Category to the Rows shelf.
2. Drag the original Sales measure to the Columns shelf. This creates your first bar chart showing total sales.
3. Now, drag your new calculated field, Sales (Selected Region), to the Columns shelf, placing it right next to the SUM(Sales) pill.
4. Right-click the SUM(Sales (Selected Region)) pill on the Columns shelf and select Dual Axis.
5. Your two charts are now overlaid. Right-click on the top axis and select Synchronize Axis to make sure they share the same scale.
6. Now, let's format the visuals. In the Marks pane, you'll see separate cards for SUM(Sales) and SUM(Sales (Selected Region)).
7. Finally, you can right-click the top axis again and uncheck Show Header to clean up the view.

At this point, you should see a gray bar chart. Don't worry that the colored bars aren't showing up yet — our Region Set is still empty! We'll hook it all up with a dashboard action next.

Step 5: Bring It All Together with a Dashboard Action

A dashboard action tells Tableau what to do when a user interacts with a sheet.

1. Create a new dashboard.
2. Drag both of your worksheets onto the dashboard: "Sales by Region Pie" and "Proportional Sales by Sub-Category."
3. Go to the top menu and select Dashboard > Actions....
4. In the pop-up window, click Add Action > Change Set Values....
5. A configuration window will appear. Fill it out as follows:
6. Click OK twice to close the actions windows.

Step 6: Test Your Dashboard!

Your interactive dashboard is now complete. Click on one of the regions in your pie chart. You should see the bar chart instantly update, showing the total sales for each sub-category in gray and overlaying the sales portion from your selected region in the color you chose. Click on another region, and it will update again. Click on the white space in the pie chart view to deselect, and the colored portion will vanish, leaving just the total sales bars. Congratulations, you've successfully created proportional brushing!

Final Thoughts

Proportional brushing is a testament to how thoughtful design can turn a good dashboard into a great one. It moves beyond simple filtering and highlighting to deliver deeper insight by always keeping crucial context in view. Mastering tools like set actions and dual-axis charts unlocks a new level of interactive data storytelling in Tableau.

Building this kind of dynamic report yourself is incredibly rewarding, but it does require navigating formulas, sets, and actions that can feel complicated. That’s why we created Graphed. Our platform is designed to short-circuit this complexity by letting you get straight to the insight using plain English. Instead of building sets and actions, you can simply ask, "Show me a dashboard of sales by sub-category in the West region, and compare it to total sales." Graphed connects to your live data sources and builds the dashboards and reports for you, turning hours of configuration into a 30-second task.