# IconArray (/docs/charts/icon-array)

IconArray answers "how likely is this, really?". A stated rate becomes countable: filled units in a fixed N-unit grid,
with the denominator visible. Two moves kill denominator neglect — the ratio label and the fixed grid. Fill order is
contiguous reading-order (scattered is harder to count), and there are **no partial-unit fills ever**: a sub-unit rate
is flagged, never faked.

```tsx
<IconArray value={0.15} total={20} title="Adverse events" width={140} height={30} />
```

## Install

```tsx
import { IconArray } from "@microcharts/react/icon-array";

<IconArray value={0.15} total={20} title="Adverse events" />
```

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** — risk in a sentence, uptake / adoption rates, lay-audience probabilities.
- **Avoid for** — a trend (Sparkline) or a full distribution (QuantileDots).


## Variants

```tsx
<IconArray value={0.1} total={10} />
<IconArray value={0.15} total={20} positive="down" />
```

```tsx
<IconArray value={0.15} total={20} label="percent" />
<IconArray value={0.6} total={10} shape="round" />
<IconArray value={0.37} total={100} label="none" />
```

## Edge cases

```tsx
<IconArray value={0} total={20} title="No adverse events" />
```

```tsx
// a real but tiny rate rounds to 0 units — flagged, never a fractional fill
<IconArray value={0.01} total={20} title="Rare event" />
```

```tsx
<IconArray value={1} total={20} title="All affected" />
```

A rate of exactly 0 draws every unit hollow. A rate that is real but rounds to 0 whole units (`note: "sub"`) still shows
a hollow grid but the summary says so explicitly — never a fractional unit standing in for "almost none." `value` is
clamped to `[0, 1]` and non-finite input renders as 0, so a bad upstream number never breaks the grid.


## Why this default

`total={20}` and `label="ratio"` are the default pairing because "3 in 20" reads faster and more honestly for a lay
audience than "15%" — the denominator stays visible instead of being computed in the reader's head. Units fill in
reading order from the top-left, never scattered: medical-risk-communication research finds scattered fills measurably
harder to count at a glance, and counting is the whole point of this chart. There is no partial-unit fill — a 37% rate
is never drawn as a unit that's 37% full, because a sub-pixel sliver of color is a precision claim this chart doesn't
make.

## Accessibility

The accessible name states the count and the rate — **"3 in 20. About 15%."** — and degenerate rates say so plainly ("0
in 20", "20 in 20 — all."). The interactive entry roves the grid in reading order with the arrow keys (2-D, row-major)
and announces each unit's state plus the running count: **"Unit 1 of 20 — filled. 3 of 20 filled."**

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 |
| --- | --- | --- |
| `value` (required) | `number` | The rate, 0–1. |
| `total` | `10 \| 20 \| 100` | Denominator / grid size (default 20). |
| `label` | `"ratio" \| "percent" \| "none"` | "3 in 20" (default) reads better than "15%" for lay audiences. |
| `shape` | `"square" \| "round" \| "dot"` | Shared cell vocabulary (default square). |
| `positive` | `"up" \| "down"` | Polarity — down (fewer is better) flips the fill to the risk tone. |
| `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).