# EnsembleGhosts (/docs/charts/ensemble-ghosts)

EnsembleGhosts answers "what could happen, across the simulated futures?". It draws a faint bundle of member paths with
one emphasized representative — because a mean line hides that futures disagree in **shape**, not just endpoint. Ghost
selection is fully deterministic (evenly spaced endpoint-rank quantiles), so the same input renders identically every
time.

```tsx
import { EnsembleGhosts } from "@microcharts/react/ensemble-ghosts";

<EnsembleGhosts
  data={[
    [40, 41, 43, 45, 47, 50],
    [40, 39, 38, 36, 35, 33],
    [40, 42, 44, 47, 49, 52],
    [40, 40, 41, 41, 42, 43],
    [40, 43, 47, 52, 56, 61],
    [40, 38, 35, 32, 30, 28],
    [40, 41, 42, 44, 45, 46],
    [40, 39, 40, 41, 42, 44],
  ]}
  endpoints
  title="Simulated futures"
/>
```

## Install

```tsx
import { EnsembleGhosts } from "@microcharts/react/ensemble-ghosts";

<EnsembleGhosts data={futures} title="Simulated futures" />
```

Setup (package + stylesheet): [Quickstart](/docs/quickstart#set-up-with-an-ai-agent) or paste [`/agent-setup.md`](/agent-setup.md) into your agent.


## When to use it

- **Good for** — a KPI card that shows the futures, not the average; Monte-Carlo / simulation output where paths
  disagree in shape; showing that outcomes fan out.
- **Avoid for** — interval precision (ForecastCone) or a single path (Sparkline).


## Variants

```tsx
<EnsembleGhosts
  data={[
    [40, 41, 43, 45, 47, 50],
    [40, 39, 38, 36, 35, 33],
    [40, 42, 44, 47, 49, 52],
    [40, 43, 47, 52, 56, 61],
    [40, 38, 35, 32, 30, 28],
  ]}
  endpoints
/>
<EnsembleGhosts
  data={[
    [40, 41, 43, 45, 47, 50],
    [40, 39, 38, 36, 35, 33],
    [40, 42, 44, 47, 49, 52],
    [40, 43, 47, 52, 56, 61],
    [40, 38, 35, 32, 30, 28],
  ]}
  emphasis="median"
/>
```

## Edge cases

```tsx
<EnsembleGhosts data={[[40, 43, 47, 52, 56, 61]]} />
```

```tsx
<EnsembleGhosts
  data={[
    [4000, 4100, 4300, 4500, 4700, 5000],
    [4000, 3900, 3800, 3600, 3500, 3300],
    [4000, 4200, 4400, 4700, 4900, 5200],
  ]}
  locale="de-DE"
/>
```

With one member, there is no bundle to show — the chart draws that single path as the representative, and the summary
states its ending value rather than a spread. A member that contains a non-finite value (`NaN`, `Infinity`) is excluded
entirely from ghost selection and the median, not gapped mid-path — a dev-only console warning flags it, since a
partially invalid future usually means bad simulation output.


## Why this default

A few faint paths and one emphasized, because a mean line hides that futures disagree in shape, not just endpoint — two
ensembles can share an average and a final range while telling completely different stories along the way. The
emphasized path defaults to the **real member** closest to the pointwise median, so the representative is an outcome
that actually happened in the simulation, not a synthetic average of paths that never occurred (`emphasis="median"`
draws that synthetic path instead). Selection and emphasis are deterministic — nothing about this chart varies between
renders of the same data. `label="end"` (default) states the emphasized path's landing value in a right gutter; pass
`label="none"` to drop it.

The static frame is not a hypothetical-outcome plot. The **loop** — flipping through the members one at a time on hover
— is the HOP, and it lives only in the interactive entry, gated on reduced motion with arrow-key stepping as the
non-animated equivalent.

## Accessibility

The accessible name states the endpoint spread and the typical path — **"5 simulated paths end between 28 and 61;
typical path ends near 50."** The interactive entry flips through the members (the HOP loop) on hover; with reduced
motion, ←/→ step them discretely, and each member is announced with its endpoint.

The interactive entry follows the shared [interaction contract](/docs/accessibility#one-interaction-contract):
arrow keys rove between units on both axes, `Home` and `End` jump to the ends, and a click, tap, `Enter` or
`Space` selects a unit — pinning its readout so it survives blur, until you select it again or press `Escape`.
On touch, a tap pins and a drag scrubs.

## Props

| Prop | Type | Description |
| --- | --- | --- |
| `data` (required) | `number[][]` | Ensemble members — 2–50 simulated paths. |
| `ghosts` | `number` | Rendered member count (deterministic endpoint-rank selection). Default 8, cap 12. |
| `emphasis` | `"nearest-median" \| "median" \| number` | A real median-like member, the synthetic median, or a pinned member. |
| `endpoints` | `boolean` | Ghost endpoint dots — makes the final-value spread countable. |
| `label` | `"end" \| "none"` | Emphasised path endpoint in a right gutter (default end). |
| `animate` | `boolean` | (interactive) Opt-in entrance motion when the chart mounts client-side — add `import "@microcharts/react/motion"` once. Inert on the server, on hydrated server HTML, and under `prefers-reduced-motion`. |

Plus the shared grammar — `data`, `domain`, `color`, `title`, `summary`, `format` — and the layout props (`width`, `height`, `className`, `style`) that every chart accepts. Interactive entries also share `animate` and `live`, and — wherever a chart has more than one navigable unit — `onActive`, `onSelect`, `selectedIndex` and `defaultSelectedIndex`; and — wherever the chart shows a hover value — `readout`. See [the shared grammar](/docs/quickstart#the-shared-grammar).