How to Edit a Parameter in Power BI

Parameters in Power BI transform your static reports into flexible, interactive tools, and knowing how to adjust them is just as important as knowing how to create them. This guide will walk you through exactly how to edit parameters in both Power Query and for "What If" scenarios on your report canvas. We'll cover the step-by-step process so you can keep your reports dynamic and relevant.

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What Are Parameters in Power BI? (A Quick Refresher)

Before jumping into editing, let's quickly clarify what parameters are. Think of a parameter as a container that holds a value. You can then reference this container throughout your report - in filters, calculations, or even to define your data source. Instead of hard-coding a value (like a specific country name or a server address), you use the parameter. This makes your reports much easier to update.

There are two main types of parameters you'll encounter, and editing them involves different steps:

• Power Query Parameters: These are created within the Power Query Editor (the "Transform Data" window). They are commonly used to filter data before it’s even loaded into your model, change data source paths (like switching from a test database to a production one), or filter a date range dynamically.
• What-If Parameters: These are created directly from the report view using DAX. They are used for scenario analysis, allowing users to interact with a slicer on the report and see how changing a variable (like a hypothetical price increase or a discount rate) would impact other visuals.

Understanding which type of parameter you're working with is the first step to editing it correctly.

Editing Parameters in Power Query

Power Query parameters are edited where they are created: inside the Power Query Editor. This is where you manipulate the data before it loads into your main Power BI data model. Let's say you built a report to analyze sales data for the 'USA', but now you need to change it to show data for 'Canada'.

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Step-by-Step Guide to Editing a Power Query Parameter

Imagine you have a parameter named p_Country that is currently set to filter your sales table for "USA". Here’s how you would edit it.

1. Open the Power Query Editor

From the main Power BI Desktop window, go to the Home tab on the ribbon and click on Transform Data. This will open the Power Query Editor, which is the heart of Power BI's data transformation capabilities.

2. Locate and Manage Your Parameters

In the Power Query Editor, look at the Queries pane on the left side of your screen. You should see your parameters listed here, often with a unique icon that looks like a gear or small slider controls. To open the main editor window, go to the Home tab within Power Query and click Manage Parameters.

This will open the Manage Parameters dialog box, which lists all the Power Query parameters in your report.

3. Edit the Parameter's Properties

Select the parameter you want to change from the list. In our example, we'll select p_Country. Now you can change any of its original settings.

Changing the Current Value

The most common edit is changing the Current Value. This is useful when you're developing a report and want to test it with different inputs without changing the fundamental structure. To change our report from analyzing USA data to Canada, you would simply type 'Canada' into the Current Value box.

Once you click OK and then Close & Apply on the main editor, Power BI will re-run the queries, this time using "Canada" to filter the sales data. Your entire report will update accordingly.

Modifying a List of Suggested Values

Parameters can also be configured with a pre-defined list of values, which restricts the input to prevent errors. What happens when your business expands and you need to add a new country to this list?

Let’s say your p_Country parameter was set up with a list containing "USA", "Canada", and "Mexico". To add "Germany", you would:

• Open the Manage Parameters dialog as described above.
• Select your p_Country parameter.
• In the Suggested Values section, make sure List of values is selected.
• You'll see the existing list. Click on an empty line at the bottom and type "Germany".
• Feel free to also change the Default Value and Current Value if needed.
• Click OK to save your changes.

Now, "Germany" is a valid option for this parameter, both for you in the editor and for any users in the Power BI service who have permission to change it.

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Editing "What If" Parameters

"What If" parameters are different beasts entirely. When you create one from the Modeling tab in Power BI Desktop, it doesn't just create a simple value placeholder. Instead, it generates a new calculated table (using a DAX function like GENERATESERIES) and an associated DAX measure.

This parameter is designed for on-the-fly scenario analysis from the report canvas. For example, you might create a "What if" parameter called Discount Percentage that generates a slicer letting users choose a value from 0% to 20% in 5% increments. You would then use the parameter's measure in another calculation, like Final Price = [Original Price] * (1 - 'Discount Percentage'[Discount Percentage Value]).

Step-by-Step Guide to Editing a What If Parameter

Because they are DAX-based, you can't edit them using the nice "Manage Parameters" window in Power Query. You have to edit the DAX code that defines them.

1. Identify the Parameter's Table

First, find the calculated table that was created by your parameter. In the Data pane on the right side of Power BI Desktop, you’ll see the table created by the What-If parameter. It often has a calculator icon next to it and a name matching what you entered during setup (e.g., "Discount Percentage").

2. View and Edit the DAX Formula

Select the table you identified. The DAX formula that generates this table will appear in the formula bar at the top of the window.

For a numeric range parameter, this formula typically uses the GENERATESERIES function. It looks something like this:

Discount Percentage = GENERATESERIES(0, 0.20, 0.05)

This formula tells Power BI to create a single-column table with numbers starting at 0, ending at 0.20 (20%), and incrementing by 0.05 (5%).

3. Modify the DAX to Your Needs

This is where you make your edits. To change the range, simply adjust the numbers inside the GENERATESERIES function.

• Start value: The first number.
• End value: The second number.
• Increment value: The third number.

Let's say you want to expand the discount range so users can select a value up to 50% (0.50). You would edit the formula to:

Discount Percentage = GENERATESERIES(0, 0.50, 0.05)

After you edit the formula and press Enter, the calculated table updates instantly. The connected slicer on your report will now show options all the way up to 50%.

You don't typically need to edit the associated measure. It uses the SELECTEDVALUE function to grab whatever value is currently selected on the slicer and usually works perfectly fine unless you rename the table or column it references.

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Practical Tips and Common Scenarios

Knowing the steps is one thing, but applying them is another. Here are a few common situations where editing parameters is essential.

• Switching Data Sources: A very common use case is using parameters for server names or file paths. You might have a parameter p_DatabaseServer with a Current Value of dev-sql-server for development. When ready to publish, you edit this parameter to prod-sql-server and republish. All your queries that reference this parameter will now pull from the production database.
• Adjusting Report Filters: Maybe you have a top-level report filter for a specific p_Year parameter. At the end of the year, you can simply edit the parameter’s Current Value to the new year to refresh your entire report for the upcoming period without rebuilding anything.
• Refining Scenarios: In a financial model, your initial What-If parameter for "Interest Rate" might range from 1% to 5%. If market conditions change, you can easily edit the DAX generating the parameter to a new, more relevant range, like 4% to 8%, keeping your analysis current.
• Troubleshooting Tip: If you edit a parameter and your data breaks or disappears, check the applied filter steps in Power Query. A common mistake is a typo in a text parameter (like 'Canad' instead of 'Canada') or a changed data type that causes a subsequent step to fail. The Power Query UI is great at helping you trace where the error occurred.

Final Thoughts

Editing parameters is a core skill for any Power BI user looking to create robust and sustainable reports. By understanding whether you're working with a Power Query or a What-If parameter, you can easily navigate to the right place - either the Power Query Editor or the DAX formula bar - to make the necessary changes and keep your analysis relevant.

While mastering the fine-grained controls of tools like Power BI is rewarding, the reality is that sometimes you just need answers from your data without spending your day inside editors and formula bars. That’s why we built Graphed. We wanted to make getting insights as simple as asking a question. You can connect sources like Google Analytics, Shopify, and Salesforce, then just ask in plain language, "Create a dashboard showing our total sales by country last quarter," and we handle the hard work of building a live, interactive visualization for you.