# WindBarb (/docs/charts/wind-barb)

WindBarb answers "which way is it flowing and roughly how hard — in one character?". The shaft points along the bearing
and the barbs count the magnitude: a half barb, a full barb, and a pennant are fixed quanta, so the glyph reads at a
glance without a scale. Quantization is the honesty here, not a limitation — the per-barb quantum is stated next to
every example.

```tsx
<WindBarb direction={225} magnitude={32} step={10} label="value" title="Wind" size={64} />
```

## Install

```tsx
import { WindBarb } from "@microcharts/react/wind-barb";

<WindBarb direction={225} magnitude={32} step={10} title="Wind" />
```

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


## Reading the barb

WindBarb has no interactive mode — a single glyph carries the whole reading, so its accessible name is the full
sentence. This gallery is the read-back key: each full barb is one `step`, a half barb is half a `step`, and a pennant
is five.

```tsx
<WindBarb direction={45} magnitude={35} />
```

```tsx
<WindBarb direction={90} magnitude={55} label="value" />
```

## When to use it

- **Good for** — wind or current direction + strength, traffic flow, net migration, request routing.
- **Avoid for** — exact magnitude (add `label`) or a time series (Sparkline).


## Variants

```tsx
<WindBarb direction={0} magnitude={1} />
```

```tsx
<WindBarb direction={45} magnitude={25} mode="arrow" />
```

```tsx
<WindBarb direction={225} magnitude={32} step={10} label="value" />
```

## Edge cases

```tsx
<WindBarb direction={0} magnitude={0} />
```

```tsx
<WindBarb direction={90} magnitude={-25} />
```

```tsx
<WindBarb direction={225} magnitude={5000} step={10} label="value" />
```

```tsx
<WindBarb direction={225} magnitude={32} step={10} label="value" format={{ maximumFractionDigits: 0 }} locale="de-DE" />
```

`format`/`locale` reach the `label="value"` numeral and the accessible summary's magnitude together — the component
builds one formatter and reuses it for both.


## Why this default

Quantized barbs read faster and more honestly than a scaled arrow whose length you'd have to measure against a legend —
the glyph is calibrated to its `step`, so counting barbs gives the magnitude directly. A near-zero magnitude renders the
conventional open circle for calm rather than a zero-length shaft, and a negative magnitude flips the bearing 180° with
a dev warning.

## Accessibility

The accessible name is the full reading — **"Southwest (225°), magnitude 32."** Calm renders as **"Calm."** Because the
glyph is self-describing, rows of barbs get their interaction from the host table or list, not from the mark.

## Props

| Prop | Type | Description |
| --- | --- | --- |
| `direction` (required) | `number` | Degrees; 0 = up/north, clockwise. |
| `magnitude` (required) | `number` | Any unit; quantized into barbs. |
| `step` | `number` | Full-barb quantum (each barb = step). |
| `label` | `"value" \| "none"` | Numeric magnitude beside the glyph. |
| `mode` | `"barb" \| "arrow"` | "arrow" swaps quantized barbs for a plain direction arrow + label. |

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).