> ## Documentation Index
> Fetch the complete documentation index at: https://docs.meerietechnology.com/llms.txt
> Use this file to discover all available pages before exploring further.

# How to build an influence diagram

> Step 2: map how inputs combine into the outcome.

The diagram shows how inputs combine into the outcome. It is generated from the same definition the engine calculates with, so the picture can never disagree with the numbers.

![Influence diagram of the Halden Foods case](https://mintcdn.com/meerie/4m98nozhN6Vq_X0_/images/user-guide/02-influence-diagram.jpg?fit=max\&auto=format\&n=4m98nozhN6Vq_X0_\&q=85\&s=f8a8334b45d90a4b4d0079ea9d6e23ae)

![Exploring the influence diagram: tracing a box and opening a module](https://mintcdn.com/meerie/4m98nozhN6Vq_X0_/images/diagram.gif?s=a8a0c29babdd91d45efd2d9c1aaef2d4)

## Reading it

Not sure what a shape or colour means? See [Types of nodes](https://docs.meerietechnology.com/structure/node-types.md).

* Ovals are uncertain or calculated values, rectangles are decisions, the diamond is the outcome.
* Each box shows its middle value. Arrow colour shows direction and thickness shows weight.
* Badges show attached evidence and whether sources support the assumed direction.
* Point at a box to trace everything it affects. Click a box or arrow for detail, evidence and research buttons.

## Editing it

Editing needs the editor role.

**1. Choose Edit diagram**

**2. Add boxes**

Pick a type from the palette (uncertain, fixed, calculation, module) and click the canvas.

**3. Draw arrows**

Drag from the handle on a box's right edge to another box.

**4. Write formulas**

Open a calculation to write its formula. Boxes with arrows into it are listed as inputs you can insert with one click. Using a variable draws its arrow; dropping it removes the arrow.

**5. Save**

Edits are a draft with undo until you choose **Save as a new version**.

**Keyboard drawing:** select a box and press **Tab** to add what it depends on, **Enter** to add another, type to name it, **Alt+Enter** to open its formula.

## Big models

Group boxes into **modules** (double-click one to open it; the breadcrumb leads back). **Group into modules by section** gives a starting point. The **Boxes** table under the diagram lists every box for finding, renaming, retyping and bulk deleting.

## Mind map

The Mind map switch shows the same model as a driver tree. **Tab** adds a driver, **Enter** another, **Ctrl+Enter** inserts a calculation, **Ctrl+G** groups the selection into a module.

> [!TIP]
>
> Keep the diagram to what actually drives the outcome. See [Best practice](https://docs.meerietechnology.com/best-practice.md).

**Next:** [Set estimates](https://docs.meerietechnology.com/estimate/set-estimates.md)


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