# Scenario Bridges
URL: https://docs.valsight.ai/scenario-bridges/
Description: A scenario bridge explains the difference between two or more scenarios, broken down by assumption, line-item or dimension.
A scenario bridge explains why two or more scenarios differ. It steps from one scenario's value to the next through the individual effects that separate them, all within one time period.

## What it is

Each scenario in the chart gets its own sum bar, and the steps in between account for the gap. What those steps represent is your choice: the assumptions that differ, the line-items behind them, or the levels of a dimension such as region or product.

![A scenario bridge stepping from one scenario's value to another through the effect of each assumption](./images/5285838946.png)

The staircase shape is what the chart editor calls a **waterfall chart**. A [time bridge](/time-bridges/) uses the same shape to explain a difference between periods rather than between scenarios.

## When to use it

* You need to explain why the realistic case lands below the plan.
* You want to show which assumptions are actually driving a gap, and which are noise.
* You want that gap broken down by region or product rather than by assumption.

Use a **[time bridge](/time-bridges/)** instead when the two values you are comparing are two points in time within a single scenario.

## Configuration

### Create the bridge

1. Click the **Chart** button in the upper right corner of a worksheet.
2. Select **Scenario Bridge** in the chart selection.

   ![Scenario Bridge in the chart type selection](./images/5285642297.png)
3. Select the node to visualize.
4. Select two or more scenarios to compare.
5. Select how the difference should be broken down: by assumptions, by line-items or by a dimension.
6. Select the time period to show.

### Change it afterwards

| Setting            | What it does                                                                                                                                                                                                                                       |
| ------------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Node**           | The node whose data the bridge shows. Change it in the chart editor at any time.                                                                                                                                                                   |
| **Scenarios**      | Which scenarios appear. Each one you add gets its own sum bar.                                                                                                                                                                                     |
| **Configure Axes** | Puts line-items, dimensions or assumptions on the axis. An assumption bridge starts with **Years** as the data series and **Assumptions** on the x-axis. A bridge broken down by a dimension starts with **Scenarios** as the data series instead. |

![The Configure Axes dialog for a scenario bridge](./images/5285740602.png)

### Break the difference down by dimension

Instead of assumptions or line-items, the steps can be the levels of a dimension, so the gap is explained by region, product or any other dimension in the model.

![A scenario bridge whose steps are dimension levels rather than assumptions](./images/5752487943.png)

There are two ways in, depending on whether the chart exists yet:

* While creating the chart, select the dimension as a delta in the configuration wizard.

  ![Selecting a dimension as a delta in the bridge configuration wizard](./images/5752356871.png)
* On an existing chart, choose the dimension in the axis configuration.

  ![Choosing a dimension in the axis configuration of an existing bridge](./images/5752160274.png)

Either way, **Enable levels as deltas** has to be switched on for the levels to be drawn as steps.

![The Enable levels as deltas setting](./images/5752553480.png)

### Show line-item variants

To break the difference down by line-item variant, select **Assumption line-items** when configuring the chart data. Each step is then labeled with both the line-item name and the variant name.

## Good to know

* **Every scenario you add is another sum bar.** A bridge across four scenarios is four sum bars with effects between each pair, which gets wide quickly. Two or three read best.
* **Dimension steps need Enable levels as deltas.** Without it the levels are drawn as ordinary values rather than as steps, which is the usual reason a dimension bridge looks wrong.
* **The steps do not have to be effects at all.** Put **nodes** on the axis instead and you get a plain build-up, for example revenue and costs stepping down to gross profit.
* **A long bridge can be shortened by grouping.** Combining the line-items of one assumption into a single bar often makes the chart readable again. See [Grouping Assumption Effects](/grouping-assumption-effects-in-bridges/).
* **Assumptions can explain themselves on hover.** Give an assumption a description and switch on the tooltip setting. See [Showing assumption descriptions](/assumption-effects/#showing-assumption-descriptions).

## Related

* [Time Bridges](/time-bridges/): the same staircase, explaining a difference between periods.
* [Assumption Effects](/assumption-effects/): how each effect is calculated, and how to show descriptions on hover.
* [Grouping Assumption Effects](/grouping-assumption-effects-in-bridges/): combine the line-items of one assumption into a single bar.
* [Bridges](/bridges/): both bridge types and the settings they share.