# Critical Path in Gantt Chart
### What is Critical Path?
The Critical Path is the longest chain of dependent tasks in a project that decides the earliest possible finish date. If any task on this path is delayed, the whole project gets delayed too.
### How Does It Work?
* Most project tools (like MS Project, Smartsheet, etc.) calculate the Critical Path by identifying:
* The task with the latest end date
* All predecessor tasks linked by dependencies (like Finish-to-Start) that lead to the task
## Displaying the Critical Path in a Gantt Chart in Power BI
To visualize the Critical Path in a Gantt chart, you first need to prepare your data using Power Query; once the critical tasks are identified, you can then display the Critical Path using a xViz Gantt chart visual in Power BI.
{% hint style="success" %}
The Critical Path is closely linked to task dependencies. To learn how task dependencies are visualized in the xViz Gantt Chart, please refer to the documentation on [Connectors](https://docs.xviz.com/project-management/connectors)
{% endhint %}
### Step 1: Create Custom Function in Power Query
1. Create a new blank query, rename it to `GetCriticalPathTasks`, and paste the below code:
```powerquery
(TaskTable as table) as list =>
let
// task with last End Date
MaxEndTask = Table.Max(TaskTable, "End Date"),
FinalTask = MaxEndTask[Task Name],
// Predecessors tasks
GetAllPredecessors = (targets as list, found as list) =>
let
step = Table.SelectRows(TaskTable, each List.Contains(targets, [Connect To]) and not List.Contains(found, [Task Name])),
newTasks = step[Task Name],
allFound = List.Union({found, newTasks}),
next = if List.IsEmpty(newTasks) then allFound else @GetAllPredecessors(newTasks, allFound)
in
next,
// list of tasks on critical path
Result = List.Distinct(List.Combine({{FinalTask}, GetAllPredecessors({FinalTask}, {})}))
in
Result
```
{% hint style="danger" %}
* Replace "End Date" with the actual column name you’re using for the task end date.
* Replace "Connect To" with the name of the column that represents the predecessor or linked task.
* Replace "Task Name" with the column name used for your project task names.
{% endhint %}
2. Navigate to the Task Table in Power Query and add a custom column that returns `1` for critical path tasks and `0` for all others using the below code:
```powerquery
if List.Contains(GetCriticalPathTasks(ChangedTypes), [Task Name]) then 1 else 0
```
{% hint style="danger" %}
Replace "Task Name" with the column name used for your project task names
{% endhint %}
This will create a new column with a value of `1` for critical path tasks and `0` for all other tasks, which can then be used in the xViz Gantt chart to visually highlight the critical path.
Image 1: Critical Path column
### Step 2: Display Critical Path in Gantt Chart
1. Now, import [xViz Gantt Chart](https://appsource.microsoft.com/en-us/product/power-bi-visuals/WA200000891) from Microsoft AppSource into your report.
{% hint style="success" %}
If this is your first time working with custom visuals, then here are the steps to [import a custom visual from Microsoft AppSource](https://learn.microsoft.com/en-us/power-bi/developer/visuals/import-visual#import-a-power-bi-visual-directly-from-appsource).
{% endhint %}
2. Populate the Display Measure Data field using the Critical Path column created in Power Query.
Image 2: Populare Critical Path Column
3. Now apply conditional formatting using the rule below to visually highlight the Critical Path.
Image 3: Apply Conditional Formatting
{% hint style="info" %}
For more details on how to apply conditional formatting in xViz Gantt chart, please refer to the documentation on [steps-to-enable-conditional-formatting](https://docs.xviz.com/project-management/alerting-techniques/steps-to-enable-conditional-formatting "mention")
{% endhint %}
As a result, the Critical Path will be highlighted, as shown in the image below:
