4.3Parameters: field parameters & what-if
The essentials in 30 seconds
- The field parameter: a slicer that swaps the measure shown (Revenue / Margin / Quantity) or the axis (by region / by product) of one visual — the multi-angle report on a single page.
- The numeric what-if parameter: a slider (e.g. % increase) whose value is read by SELECTEDVALUE and injected into the measures to simulate.
- Power Query parameters make the source configurable (path, year): two worlds, two menus — source on one side, analysis on the other.
Running mini-case — Zineb gives her management a chameleon report
Zineb, a management controller at an agri-food SME in Algiers, is drowning in pages: one per measure (Revenue, margin, quantity) and one per axis (region, product). Instead of multiplying pages, she applies the method. She creates a field parameter (Modeling → New parameter → Fields) with [Total revenue], [Sales count], [Average basket]: a slicer swaps the measure shown in her bar chart. She adds an axis parameter (Region, Product, Salesperson): the same visual pivots. Then she creates a what-if "Increase %" (0 to 20) and the measure Simulated revenue = [Total revenue] * (1 + 'Increase %'[Increase % Value] / 100), placed next to the real revenue: management can test a scenario. She has replaced entire pages with a single controllable visual.
Standalone case for this section: it returns in the course, the diagram, the script and the 48h challenge of section 4.3.
1. The field parameter: the chameleon visual
The field parameter (Modeling → New parameter → Fields) creates a list of measures or columns that a slicer can swap in a visual. You drag the parameter onto the axis: the slicer then changes the measure shown (Revenue / Margin / Quantity) or the axis (by region / by product). A single visual, several angles — two pages saved. Zineb places the parameter on the Y-axis of her bar chart.
2. What-if: simulate
The what-if parameter (New parameter → Numeric range) creates a slider whose value is read by SELECTEDVALUE and injected into the measures. Example: Simulated revenue = [Total revenue] * (1 + 'Increase %'[Increase % Value] / 100). You place the real and the simulated side by side: management tests "what if we increase by 10%?". SELECTEDVALUE is the slicer → DAX gateway.
3. Power Query parameters
Don't confuse two worlds. Power Query parameters (in the query editor) make the source configurable — file path, year, environment — without rewriting the steps. Model parameters (field, what-if) serve analysis. Zineb puts her source path in a Power Query parameter and her analysis angles in model parameters: two menus for two needs.
🔎 Concrete example — 🔎 Concrete example — The what-if simulator
Zineb has management test a hypothesis:
New parameter → Numeric range "Increase %" (0 to 20, step of 1)
Simulated revenue = [Total revenue] * (1 + 'Increase %'[Increase % Value] / 100)
→ [Total revenue] and [Simulated revenue] side by side with the slider: simulated scenario.Reading: the slider doesn't change the data: it feeds a simulation measure.
Lesson: SELECTEDVALUE connects the what-if slicer to DAX.
Section vocabulary
- Field parameter
- Modeling → New parameter → Fields: the list of measures/columns that a slicer can swap in the visuals.
Simple example: Zineb alternates between revenue, margin and quantity on the same bar chart.
What it is not: creating one page per measure.
Reflex: one visual, several measures → field parameter.
- What-if parameter (numeric)
- Modeling → New parameter → Numeric range: a slider whose value (SELECTEDVALUE) is used in the measures.
Simple example: Zineb sets an increase of 0 to 20% with the slider.
What it is not: a hypothesis frozen in the formula.
Reflex: simulate a scenario → what-if.
- SELECTEDVALUE
- The function that reads the parameter's chosen value: Simulated revenue = [Total revenue] * (1 + 'Increase %'[Increase % Value] / 100).
Simple example: Zineb reads it to wire the slider to DAX.
What it is not: a constant hard-coded.
Reflex: slicer → DAX goes through SELECTEDVALUE.
- Power Query parameter
- A query parameter (file path, environment): the source becomes configurable without rewriting the steps.
Simple example: Zineb exposes her source path as a reusable parameter.
What it is not: a path hard-coded in the query.
Reflex: configure the source → Power Query.
- Driven report
- The result: the user chooses the angle, the measure, the scenario — the same report serves ten analyses.
Simple example: Management explores revenue/margin and simulates an increase.
What it is not: a page frozen per question.
Reflex: fewer pages, more control.
In practice — In practice — The chameleon visual and the simulator
- Field parameter: Modeling → New parameter → Fields → check [Total revenue], [Sales count], [Average basket] → the slicer is created. Drag the parameter onto the Y-axis: the slicer changes the displayed measure.
- Double it with an axis parameter: Region, Product, Salesperson — the same visual pivots across three angles.
- What-if: New parameter → Numeric range "Increase %" (0 to 20, step of 1). Create: Simulated revenue = [Total revenue] * (1 + 'Increase %'[Increase % Value] / 100).
- Place [Total revenue] and [Simulated revenue] side by side with the slider: the scenario simulator is born.
Step-by-step script — driving the report like Zineb (7 min)
1) Modeling → New parameter → Fields: check [Total revenue], [Sales count], [Average basket] and confirm — a slicer is created. 2) Drag this parameter onto the Y-axis of your bar chart: change the slicer value, the displayed measure changes. 3) Create an axis parameter (Region, Product, Salesperson) and place it on the X-axis: the visual pivots. 4) New parameter → Numeric range "Increase %" (0 to 20). 5) Write Simulated revenue = [Total revenue] * (1 + 'Increase %'[Increase % Value] / 100) and place it next to the real revenue with the slider.
Rename the field parameter labels (Table view): "Revenue (DZD)" rather than "Total revenue" — cleaner for the user.
Copy-paste template — my parameters
Field parameter: Modeling → New parameter → Fields
Measures: [Total revenue], [Sales count], [Average basket]
Axes : Region, Product, Salesperson
What-if: New parameter → Numeric range "Increase %" (0-20)
Simulated revenue = [Total revenue] * (1 + 'Increase %'[Increase % Value] / 100)
Power Query = source; model = analysis. 1-3 levers maximum.Chameleon visual
Zineb alternates between revenue, margin and quantity on the same bar chart via a field parameter.
Interchangeable axes
Zineb pivots the same visual by region, product or salesperson without a new page.
Simulator
Zineb places the real revenue and the simulated revenue side by side: management tests an increase.
Parameterized source
Zineb exposes the file path as a Power Query parameter to change year without rewriting.
✓ Best practices
- Rename the field parameter labels ("Revenue (DZD)" rather than "Total revenue").
- Use SELECTEDVALUE to wire the what-if slider into the measures.
- Distinguish Power Query parameters (source) from model parameters (analysis).
✗ Common pitfalls
- Multiplying what-if sliders (beyond 2-3 levers, usability degrades).
- Confusing a source parameter with an analysis parameter.
- Forgetting to set the order of the entries (index column).
Key takeaways
- The field parameter swaps measures or axes of a visual: the multi-angle report on one page.
- What-if injects a slider into the measures: instant simulation.
- SELECTEDVALUE reads the user's choice: the slicer → DAX gateway.
- Power Query parameters for the source, model parameters for the analysis.
48h challenge — apply it tomorrow
Like Zineb, create a field parameter that swaps two measures on the same visual, then a what-if "Increase %" with the Simulated revenue measure (SELECTEDVALUE). Place the real and the simulated side by side and write in one sentence the scenario your management would test.
- I can create a field parameter that changes the measure or the axis of a visual.
- I know how to build a what-if and wire SELECTEDVALUE into a measure.
- I distinguish Power Query parameters (source) from model parameters (analysis).
Frequently asked questions
Can I rename the field parameter entries (clean labels)?
Yes: the parameter table is editable (Table view). Modify the labels column ("Revenue (DZD)" instead of "Total revenue") and set the order via the index column for a polished slicer, presented in a logical order.
Can what-if exceed 3 variables?
Technically yes (one parameter per variable), but usability degrades quickly. Beyond 2-3 levers, change tool: a real simulation model (Excel/solver) or precomputed scenarios.
What does a field parameter do?