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# Analytics

Critical path and slack computed over a schedule's dates. It's the `analytics` field of [`ScheduleResult`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/results/schedule-result.md>). That field is `Some` only when the call's [`AnalyticsOptions`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/project/analytics-options.md>) set `critical_path`, `slack`, or both. With both `false`, it's `None`.

## Declaration

```rust
#[derive(Clone, Debug, PartialEq)]
pub struct Analytics {
    pub status: AnalyticsStatus,
    pub critical_path: Option<Critical>,
    pub slack: Option<Vec<TaskSlack>>,
}
```

With the `serde` feature, `Analytics` implements `Serialize` and `Deserialize`. Fields use camelCase (`criticalPath`), and `None` fields are left out. See [Serialize results to JSON](<https://docs.dhtmlx.com/planning-engine/rust/how-to/serialize-results-to-json.md>).

## Fields

| Field | Type | Description |
|---|---|---|
| `status` | [`AnalyticsStatus`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/results/analytics-status.md>) | Whether the analytics could be computed. |
| `critical_path` | `Option<`[`Critical`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/results/critical.md>)`>` | Critical tasks and links. `Some` when [`AnalyticsOptions::critical_path`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/project/analytics-options.md>) is `true` and `status` is `Available`. |
| `slack` | `Option<Vec<`[`TaskSlack`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/results/task-slack.md>)`>>` | Total and free slack per task. `Some` when `AnalyticsOptions::slack` is `true` and `status` is `Available`. |

With `status` set to `AnalyticsStatus::Invalid`, both `critical_path` and `slack` are `None`, whatever the options asked for. Check `status` before reading the other fields.

## Example

Requests the critical path and slack for three tasks and prints both.

```rust
use plen_core::{
    schedule, AnalyticsOptions, AnalyticsStatus, DateTime, LinkData, LinkType, ProjectData,
    SolveOptions, TaskData,
};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let monday = DateTime::from_ymd_hm(2026, 1, 5, 8, 0).ok_or("invalid date")?;

    let mut design = TaskData::new("design");
    design.start_date = Some(monday);
    design.duration = Some(2.0);

    let mut build = TaskData::new("build");
    build.start_date = Some(monday);
    build.duration = Some(3.0);

    let mut docs = TaskData::new("docs");
    docs.start_date = Some(monday);
    docs.duration = Some(1.0);

    let data = ProjectData {
        tasks: vec![design, build, docs],
        links: vec![LinkData {
            id: "l1".into(),
            source: "design".into(),
            target: "build".into(),
            link_type: LinkType::Fs,
            lag: 0.0,
            lag_unit: None,
        }],
        ..Default::default()
    };
    let options = SolveOptions {
        analytics: AnalyticsOptions {
            critical_path: true,
            slack: true,
        },
        ..Default::default()
    };

    let result = schedule(data, &options)?;
    let analytics = result.analytics.ok_or("analytics not requested")?;

    if analytics.status == AnalyticsStatus::Invalid {
        println!("the dependency graph has a cycle");
        return Ok(());
    }
    if let Some(critical) = &analytics.critical_path {
        println!("critical tasks: {:?}", critical.tasks);
    }
    for s in analytics.slack.iter().flatten() {
        println!("{}: total {}, free {}", s.task, s.total, s.free);
    }
    Ok(())
}
```

## Related

- [`AnalyticsOptions`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/project/analytics-options.md>) - selects which analytics are computed
- [`ScheduleResult`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/results/schedule-result.md#analytics>) - holds the analytics of a call
- [`SolveOptions`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/project/solve-options.md#analytics>) - passes the analytics request to `solve`
- [Critical path and slack](<https://docs.dhtmlx.com/planning-engine/rust/scheduling/critical-path-and-slack.md>) - requests and reads analytics