# Driver Editor Screen

This article explains the **Driver Editor screen** in Model Reef.

You will learn:

* What a driver is in Model Reef.
* How to view and edit driver time series.
* How drivers connect to variables and formulas.

Drivers provide reusable inputs that shape variable behaviour across the model.

{% stepper %}
{% step %}

### What the Driver Editor is for

Where the Variable Editor controls a single variable's behaviour, the Driver Editor controls shared **input series**, such as:

* Market growth rates.
* Unit prices.
* Volumes, headcounts or utilisation.
* FX rates or inflation.
* Seasonality indices.
* Other modifiers used in formulas.

Changing a driver can affect many variables at once.
{% endstep %}

{% step %}

### Opening the Driver Editor

You can open the Driver Editor from:

* The drivers list within a branch or model.
* The Data Library viewer when you open a driver entry.
* A formula or variable that references a driver (via drill down).

Once open, you see the full time series for that driver across the model timeline.
{% endstep %}

{% step %}

### Driver types

Model Reef groups drivers into three main classes:

* **Economic drivers**
  * Prices, inflation, FX, macro indices and similar.
* **Operational drivers**
  * Units, volumes, hours, headcount, utilisation and so on.
* **Modifier drivers**
  * Percentages, scalars, adjustment factors and scenario modifiers.

The driver type is mostly for clarity and organisation. It does not by itself create P\&L or cashflow entries until a variable uses the driver.
{% endstep %}

{% step %}

### Editing driver values

In the Driver Editor you can:

* Enter values directly by period.
* Apply preset patterns such as growth, flat ranges or seasonal shapes.
* Import historical series from the Data Library or external sources.
* Copy and paste ranges from spreadsheets if needed.

Changes you make here update all variables and formulas that reference the driver.
{% endstep %}

{% step %}

### Timing, frequency and interpolation

Drivers use the model's base periodicity, but you can:

* Define driver values at a coarser level and have Model Reef interpolate.
* Use schedules to apply different values in different periods.
* Apply seasonality patterns to repeat over each year.

For many use cases, drivers are smoother than variables and act as simple, intuitive assumption series.
{% endstep %}

{% step %}

### Linking drivers to variables and formulas

Variables and formulas can use drivers in several ways:

* Direct multiplication, for example `Revenue = Units driver × Price driver`.
* Adjustment factors, for example `Opex = Base cost × Inflation driver`.
* Scenario toggles, for example `Volume × Scenario modifier driver`.

The Driver Editor does not show all uses of a driver, but you can usually drill down from variables to see which drivers they reference.
{% endstep %}

{% step %}

### Documentation and collaboration

As with variables, you can:

* Add notes explaining what the driver represents and where the numbers come from.
* Attach source files, such as market reports or CSVs.
* Tag the driver for review or ownership.

Because drivers can affect many variables, good documentation here is particularly important.
{% endstep %}
{% endstepper %}

## Related articles

* [Selecting Driver Type](/syntax/drivers-syntax/selecting-driver-type.md)
* [Overriding Variables](/syntax/scenario-syntax/overriding-variables.md)
* [Accrual Logic](/help/drivers-variables-and-timing/accrual-logic.md)
* [Build a Driver Based Forecast](/how-tos/core-modelling/build-a-driver-based-forecast.md)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://help.modelreef.io/syntax/understanding-the-interface/driver-editor-screen.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.