How to Make a Radar Chart in Tableau

While Tableau is a powerhouse for data visualization, it doesn't give you a one-click option to create a radar chart. This means you have to build one from the ground up, but a little bit of custom-building can show you just how powerful Tableau's calculation engine really is. This article will walk you through the entire process, starting with the data structure and trigonometry, and ending with a polished, presentation-ready chart.

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What is a Radar Chart?

A radar chart - also known as a spider chart, web chart, or star plot - is a visual representation for comparing multiple variables. It looks like a spider's web, with each variable represented by an axis that radiates from the center. A line is then drawn connecting the data points for each axis, creating a unique "shape" for each set of data.

They are especially useful when you want to see how one or more items stack up against several different performance metrics. For example, you could use a radar chart to:

• Compare the feature set of two competing products.
• Evaluate an employee's skills across different competencies.
• Analyze the performance of different marketing campaigns across metrics like clicks, conversions, and cost-per-acquisition.

The main benefit is that it makes it easy to spot outliers and similarities at a glance. You can quickly see which product is more "well-rounded," which employee has a specialized skill set, or which campaign is outperforming others overall.

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Preparing Your Data for a Tableau Radar Chart

Before you even open Tableau, you need to make sure your data is structured properly. Radar charts require a "tall" data format rather than a "wide" one. Instead of having each variable (or metric) in its own column, you want a column for the name of the variable and another for its value.

Let's say we're comparing two social media platforms, "Platform A" and "Platform B," across five metrics: Engagement, Reach, Followers, Post Frequency, and Ad Spend.

A "wide" format (less ideal) would look like this:

For Tableau, you want to pivot this into a "tall" format (ideal):

If your data is already in Tableau in the "wide" format, you can easily pivot it. Just go to your data source, select the columns you want to pivot (like Engagement, Reach, etc.), right-click, and select "Pivot." Tableau will create the "Pivot Field Names" (your Metrics) and "Pivot Field Values" (your Scores) columns for you.

Step-by-Step: Building Your Radar Chart

This is where things get interesting. Creating a radar chart involves using a little trigonometry to plot points in a circle. Don't worry if you haven't thought about sine or cosine since high school - we'll lay out the exact formulas you need. The core concept is that we're converting angles and values into X and Y coordinates on a graph.

Step 1: Create the Necessary Calculated Fields

In your Tableau worksheet, you'll need to create a few calculated fields. For this example, let's assume we're using our social media data with the dimensions [Platform] and [Metric] and the measure [Score].

1. Index This calculation numbers our metrics from 1 to 5 (since we have 5 metrics). This ordering is crucial for placing the points correctly around the circle.

INDEX()

2. Number of Metrics This calculation simply counts how many different metric points we need to plot for each platform. It will be used to determine the angle for each point.

WINDOW_COUNT(COUNTD([Metric]))

3. Angle This is where the math kicks in. We take the full circle (2 * PI) and divide it by the total number of metrics. We then multiply that by the index of the current metric to get its position on the circle.

( [Index] / [Number of Metrics] ) * 2 * PI()

Note: Tableau needs the angles in radians, which is why we use PI().

4. X-Coordinate Now we calculate the final X position for our point. We use the cosine of the angle and multiply it by the score for that metric. This scales the point's distance from the center.

[Score] * COS([Angle])

5. Y-Coordinate Similarly, we use the sine of the angle to calculate the Y position for the point.

[Score] * SIN([Angle])

You should now have five new calculated fields. Make sure to save your work!

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Step 2: Building the Chart in the Worksheet

With our calculations ready, we can start putting the visual together.

1. Drag the [X-Coordinate] calculated field to the Columns shelf.
2. Drag the [Y-Coordinate] calculated field to the Rows shelf.
3. Place the [Platform] dimension onto the Color shelf in the Marks card. This will create separate charts for Platform A and Platform B.
4. Place the [Metric] dimension onto the Detail shelf in the Marks card. You'll see a scatter plot of points start to take shape.
5. Change the Mark Type from "Automatic" (or "Circle") to "Polygon". This will tell Tableau to connect the dots and fill in the shape.
6. Drag the [Metric] dimension onto the Path shelf. This tells Tableau the order in which to connect the points to form the polygon shape.

At this point, you'll see something on your canvas, but it probably doesn't look right. That's because we need to configure our table calculations.

Step 3: Configure the Table Calculations

Right-click the [X-Coordinate] pill on the Columns shelf and select "Edit Table Calculation." This is the most important step.

• In the Table Calculation dialog box, you'll see a dropdown for "Nested Calculations." You need to set the computation for EACH nested calculation (Index and Number of Metrics).
• Select Index from the dropdown and set "Compute Using" to Specific Dimensions, then check the box for Metric.
• Now, select Number of Metrics from the dropdown and do the same: "Compute Using" Specific Dimensions, and check Metric.

Repeat this entire process for the [Y-Coordinate] pill on the Rows shelf. Once done, your points should arrange themselves into a recognizable radar chart shape!

Finally, right-click on both the X and Y axes and select "Edit Axis." Set the ranges to be fixed, for example, from -100 to 100 on both, to make the chart symmetrical. You can also hide the axis headers by right-clicking each pill and deselecting "Show Header."

Adding a Background Web and Labels

A true radar chart has a background "web" of concentric circles to make it easier to judge the values. This takes a little extra work in Tableau, as it involves creating a background image or layering two worksheets on a dashboard.

A simple dashboard method works well:

1. Create the Background Chart: Design the gray radial lines you usually view with charts like this in RStudio or Photoshop. Then, in Tableau, create a new simple sheet and insert the background into a box as a full-width image container. This is simple and effective.
2. Use Custom Backgrounds in R or Python instead: For those wanting a seamless, dynamic approach without managing external images, leveraging R or Python integration within Tableau offers a powerful alternative. You can programmatically generate circular or polygonal grid lines as a background layer and finally bring that image over as done in the earlier step.

To add metric labels, drag the [Metric] dimension to the Label shelf on the Marks card. You may need to manually adjust their position so they sit cleanly on the outer points of the chart.

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Final Touches and Best Practices

Once your chart is built, here are a few ways to make it more effective:

• Adjust Opacity: Drop the opacity of the Polygon mark to around 70%. If you have overlapping shapes (for example, comparing three or more things), this ensures you can see all the data.
• Add Tooltips: Clean up the tooltip by dragging [Platform], [Metric], and [Score] to the Tooltip shelf. You can format it to be clear and informative on hover. Example: "Platform: <Platform>, <br> Metric: <Metric>, <br> Score: <Score>."
• Be Mindful of Clutter: Radar charts get messy with too many variables or too many items being compared. They are best for 5-10 variables and no more than 3-4 items. If you have more, a bar chart might be a better choice.

Final Thoughts

Building a radar chart in Tableau is a perfect example of its incredible flexibility. While it feels complex at first, the aforementioned building process actually teaches you the fundamental logic of the Tableau visualization engine and is applicable across many more complex visualization tasks using the native Tableau feature set. Ultimately, what at first glance looks like a manual chart drawing exercise will quickly train you into a data native visualization expert, where the answer to "what could I build" will get clearer and clearer as you gain experience doing custom development like this in Tableau.

If you're looking for a faster way to get performance insights without the trigonometry, that's precisely why we built Graphed. We wanted to eliminate the steep learning curve and constant manual work associated with complex analytics. Instead of creating calculated fields and editing table calculations, you can connect your data sources and simply ask your question in plain English like "Show me a chart comparing marketing channels across KPIs of leads, lead conversion rate, and lead to customer rate for Platform A vs Platform B," and then get a beautiful chart just seconds later. It feels more like having a conversation because our goal is to free up your time to focus more attention on answering bigger, "what's next?" questions that drive actual business value.