# QuantileDots (/docs/charts/quantile-dots)

QuantileDots answers "what are the odds?" — in **countable** form. It's a quantile dotplot: each dot is an
equal-probability quantile, so a dot is roughly a **1-in-N chance**, not a raw observation. Add a `threshold` and the
plot turns from shape into odds: the dots past the line are re-inked and ringed, and the summary reads **"N in 20"** —
because odds you can count beat odds you must trust, and a frequency reads truer than a bare percentage.

```tsx
<QuantileDots
  data={Array.from({ length: 200 }, (_, i) =>
    Math.round(4 + (i % 30) * 0.35 + ((i * 7) % 13) * 1.1 + (i % 50 === 0 ? 20 : 0)),
  )}
  threshold={15}
  format={{ style: "unit", unit: "minute", unitDisplay: "short", maximumFractionDigits: 0 }}
  title="Bus wait"
  width={260}
  height={30}
/>
```

## Install

```tsx
import { QuantileDots } from "@microcharts/react/quantile-dots";

<QuantileDots data={waits} threshold={15} format={(n) => `${n} min`} title="Bus wait" />
```

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 "will we miss the SLA?" read in a sentence, odds you can count in a KPI card, a posterior
  communicated as frequency rather than percent.
- **Avoid for** — a precise distribution shape (HistogramStrip) or one estimate's interval (GradedBand).


## Variants

```tsx
<QuantileDots data={waits} count={15} threshold={15} />
<QuantileDots data={waits} threshold={10} side="below" />
```

`format` also takes `Intl.NumberFormatOptions` — with a `locale`, the announced threshold follows that locale's own
grouping and decimal marks.

```tsx
<QuantileDots
  data={waits}
  threshold={15000}
  format={{ style: "unit", unit: "minute", unitDisplay: "narrow" }}
  locale="de-DE"
/>
```

## Edge cases

```tsx
<QuantileDots data={[]} title="No samples" />
```

```tsx
<QuantileDots data={[7, 7, 7, 7, 7]} title="Certain outcome" />
```

```tsx
<QuantileDots data={waits} threshold={9999} side="above" />
```

Empty data draws nothing and the summary says so plainly. An all-equal sample collapses every dot into one column —
genuine certainty, not a rendering glitch. A threshold outside the observed range reads as 0 in N (or N in N) — the
count is always honest about what fraction of the field it's actually catching.


## Why this default

20 dots, because odds you can count beat odds you must trust — a reader subitizes a handful of highlighted dots faster
than they parse "48%". Each dot is an equal-probability quantile, **not** a raw observation, and the summary always
frames the answer as a frequency ("10 in 20"), never a bare percentage. Dots past the threshold are re-inked **and**
ringed, so the count survives grayscale, print, and forced-colors.

## Accessibility

The accessible name states the odds in frequency form — **"8 in 15 chances above 15 min."** — or, without a threshold,
"Most likely …; range …". The interactive entry is a probe: hovering or arrowing moves a live threshold and the count
past it recomputes as you go.

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[]` | Raw sample or posterior draws — the component derives the quantile dots. |
| `count` | `number` | Number of quantile dots (default 20; 15–20 recommended; capped at 25). |
| `threshold` | `number` | The decision line — turns the plot from shape into odds. |
| `side` | `"above" \| "below"` | Which side of the threshold is the event being counted. |
| `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).