How to Add Trendline in Scatter Plot Power BI

Adding a trendline to a scatter plot is a fast and effective way to see the underlying relationship in your data. It cuts through the noise of individual data points to show you the bigger picture. This tutorial will walk you through exactly how to create a scatter plot in Power BI and add a trendline to start uncovering valuable insights.

First, What Is a Scatter Plot?

Before we add a trendline, let's quickly review what a scatter plot does. A scatter plot (or scatter chart) is a data visualization that uses dots to represent the values for two different numeric variables. One variable is plotted on the horizontal axis (X-axis), and the other is plotted on the vertical axis (Y-axis).

The main purpose of a scatter plot is to see the relationship - or correlation - between two variables. You can quickly see if there's a connection, what kind of connection it is, and how strong it is.

For example, you might use a scatter plot to analyze:

• The relationship between advertising spend and sales revenue.
• How customer age correlates with average order value.
• Whether there’s a link between website loading speed and bounce rate.

By plotting these data points, you can spot patterns, clusters of data, and outliers that might be impossible to notice in a spreadsheet or table.

What is a Trendline (and Why Is It Useful)?

A trendline, often called a "line of best fit," is a straight or curved line on a chart that shows the general direction or pattern of your data points. Instead of focusing on each individual dot, the trendline gives you a clear, simple visualization of the overall trend.

Adding a trendline is useful for a few key reasons:

• Identifying Trends Easily: It instantly shows whether the variables have a positive correlation (as one increases, the other tends to increase), a negative correlation (as one increases, the other tends to decrease), or no correlation at all.
• Making Predictions: While not a formal forecasting tool, a trendline can help you make informal predictions about what might happen. If you see a strong positive trend between ad spend and conversions, you might reasonably expect that increasing ad spend would lead to more conversions.
• Communicating Insights: A scatter plot full of dots can sometimes look like a random mess to stakeholders. A trendline adds immediate clarity, making it easy for anyone to understand the key takeaway from the chart.

Step-by-Step: Adding a Trendline to Your Power BI Scatter Plot

Now, let's get into the practical steps. Adding a trendline in Power BI is straightforward once you know where to look. We’ll start by creating a simple scatter plot and then add our trendline. For this example, let’s imagine we’re an e-commerce store analyzing the relationship between the number of product photos on a page and the number of units sold.

Step 1: Create a Basic Scatter Plot

First, you need the scatter plot visual on your report canvas. If you already have your plot, you can skip to the next step.

1. Open your report in Power BI Desktop.
2. In the Visualizations pane on the right, find and click on the scatter chart icon. It looks like a grid of dots.
3. An empty visual will appear on your report canvas. With the visual selected, turn to the Fields pane (which shows your data tables).
4. Drag your independent variable (the one you think might influence the other) to the X-Axis well. In our example, this would be ‘Number of Product Photos.’
5. Drag your dependent variable (the one you are measuring) to the Y-Axis well. For us, this is ‘Units Sold.’

You should now have a scatter plot showing a collection of dots, with each dot representing a product.

Step 2: Open the Analytics Pane

This is where the magic happens. The feature to add trendlines and other analytical visuals isn't in the generic 'Format your visual' section (the paintbrush icon). Instead, you need the Analytics pane.

1. Make sure your scatter plot visual is selected on the canvas.
2. In the Visualizations pane, look for a small icon that looks like a magnifying glass to the right of the ‘Format your visual’ painter's brush icon.
3. Click on the magnifying glass icon to open the Analytics pane.

This pane contains a variety of options for adding analytical lines to your visual, including the one we need.

Step 3: Add and Enable the Trendline

Now that you're in the Analytics pane, adding the line is just a few clicks away.

1. You'll see a list of different analytical lines you can add. Scroll down until you find Trend line.
2. Click on the "Trend line" header to expand its options.
3. Click the + Add button.

That's it! A new trendline will instantly appear on your scatter plot, representing the general relationship between your X and Y axis variables.

Customizing Your Power BI Trendline

Once you've added the trendline, Power BI offers several customization options within the same Analytics pane to help it match your report’s style or make it easier to interpret.

Change the Style

Under the "Style" dropdown, you can change the appearance of the line itself. Your options are:

• Solid: A standard, continuous line (the default).
• Dashed: A line made of small dashes.
• Dotted: A line made of small dots.

Dashed or dotted lines can be useful if your chart is quite busy, helping the trendline feel less visually dominant than other elements.

Adjust Color and Transparency

You can change the trendline’s Color to anything you want. It's good practice to either align it with your brand colors or choose a color that stands out clearly from the data points. You can also adjust the Transparency slider to make the line more or less opaque.

Combine Series

This is an important option if your scatter plot uses a legend. For example, if you dragged a ‘Product Category’ field into the Legend well of your scatter plot, you'd have different colored dots for each category (e.g., Electronics, Clothing, Home Goods).

• Combine Series (Off): By default, this is off. In this case, Power BI will create a separate trendline for each series in your legend. This is useful for comparing the trends between different categories. You might find that for electronics, adding more photos has a strong positive effect, while for clothing, it has a weaker effect.
• Combine Series (On): If you switch this on, Power BI will ignore the different series and draw a single trendline that represents the overall trend across all your data points combined.

Understanding What Your Trendline Means

Adding the line is easy, but the real value comes from interpreting it. Here’s a quick guide to what the slope of your line is telling you.

Positive Correlation (Upward Sloping Line)

If your trendline goes up from left to right, it indicates a positive correlation. This means that as the value on the X-axis increases, the value on the Y-axis also tends to increase. Example: Sales revenue tends to increase as the advertising budget increases.

Negative Correlation (Downward Sloping Line)

If your trendline goes down from left to right, it indicates a negative correlation. As the value on the X-axis increases, the value on the Y-axis tends to decrease. Example: The number of units sold tends to decrease as the price of a product increases.

No Correlation (Flat or Near-Flat Line)

If your trendline is mostly flat, it suggests there is little to no linear relationship between the two variables. An increase in one variable doesn't have a predictable effect on the other. Example: The number of followers on your company's Instagram account probably has no relationship with the average daily temperature in your city.

Quick Word of Caution: Remember that correlation does not equal causation. A trendline can show you that two variables move together, but it can’t prove that one is causing the other to change. There could be another hidden factor influencing both. Always use this as a starting point for deeper investigation, not as a final conclusion.

Beyond the Trendline: Other Helpful Analytical Lines

The Analytics pane in Power BI has a few other useful lines that can add even more context to your visualizations.

• Constant Line: Adds a perfectly horizontal or vertical line at a value you specify. This is great for showing a target or an important threshold. For example, you could add a constant line on the Y-axis for your monthly sales goal.
• Average Line: Automatically calculates and plots a line showing the average of all the points on your X or Y-axis. This gives you a quick baseline to see how individual points perform against the average.
• Min & Max Lines: Just like the average line, these will plot lines at the minimum or maximum values in your dataset, which is helpful for seeing the entire range of your data's performance.

Feel free to experiment with these lines. They can be combined with trendlines to create information-rich visuals that tell a more complete story.

Final Thoughts

Adding a trendline to a Power BI scatter plot is a simple action that delivers powerful insights, visually summarizing the relationship between two variables at a glance. By using the Analytics pane, you can quickly add and customize this feature to turn a simple chart into a compelling piece of analysis that highlights important trends in your business data.

Manually building these analyses in BI tools can often feel like a hunt for the right setting in the right panel. With Graphed, we’ve made getting to the insight much more direct. You can simply ask for what you need in plain English - like "show me the relationship between ad spend and sessions from Facebook Ads, and add a trendline" - and the chart is built for you instantly. This helps turn data analysis into a conversation, so you spend less time clicking and more time acting on what you discover.