# GradeProfile (/docs/charts/grade-profile)

GradeProfile answers "how hard is this route, and where does it bite?" Each segment between two points is filled from
the baseline and coloured by its grade — gentle to brutal — with the elevation ridge riding on top. The steepest pitch
is called out, so the wall in the route is the first thing you see.

**How to read it** — colour is a _quantized_ grade bin, never a smooth ramp: flats and every descent take the faint
band, then a mid tone, the negative colour, and the darkest fill for the brutal pitches. Height is the elevation ridge
for shape; the encoded channel is the colour, and the interactive readout gives the exact grade.

```tsx
<GradeProfile
  data={[
    { d: 0, elev: 800 },
    { d: 100, elev: 809 },
    { d: 250, elev: 812 },
    { d: 350, elev: 817 },
    { d: 500, elev: 835 },
    { d: 700, elev: 833 },
    { d: 900, elev: 865 },
  ]}
  format={{ style: "unit", unit: "meter", unitDisplay: "short" }}
  title="Queen stage"
  width={240}
  height={48}
/>
```

`d` and `elev` must share a unit (both metres, say) so that grade — rise ÷ run — is a true percent. Distance need only
be monotonic; the values themselves can be any scale.

## Install

```tsx
import { GradeProfile } from "@microcharts/react/grade-profile";

<GradeProfile data={trail} format={(n) => `${n} m`} title="Queen stage" />
```

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** — route and climb profiles (cycling, running, hiking); showing _where_ the hard pitches fall.
- **Avoid for** — a single elevation series (Sparkline), or an unordered track (distance must be monotonic).


## Variants

```tsx
const trail = [
  { d: 0, elev: 800 }, { d: 250, elev: 812 }, { d: 500, elev: 835 },
  { d: 700, elev: 833 }, { d: 900, elev: 865 },
];

<GradeProfile data={trail} label="none" />
```

```tsx
// classify the difficulty differently: brutal starts at 12%
const trail = [
  { d: 0, elev: 800 }, { d: 100, elev: 809 }, { d: 350, elev: 817 },
  { d: 500, elev: 835 }, { d: 900, elev: 865 },
];

<GradeProfile data={trail} bins={[5, 8, 12]} />
```

```tsx
const alps = [
  { d: 0, elev: 600 }, { d: 2000, elev: 780 }, { d: 5000, elev: 1150 },
  { d: 8000, elev: 1400 }, { d: 12000, elev: 1850 },
];

<GradeProfile data={alps} format={{ maximumFractionDigits: 0 }} locale="de-DE" />
```

`format` accepts `Intl.NumberFormatOptions` (with a `locale`) or a formatting function, and applies to **distance and
elevation** numbers in the summary and readout — not grade. Grades are always percent-encoded; the locale still decides
the decimal mark: the alpine profile above reads **"12.000, 1.250 gain; steepest 12,3% at 3.500."** in German.

## Edge cases

```tsx
const drop = [{ d: 0, elev: 900 }, { d: 300, elev: 840 }, { d: 600, elev: 780 }];

<GradeProfile data={drop} format={(n) => `${n} m\
```

```tsx
const gappy = [
  { d: 0, elev: 100 }, { d: 100, elev: 120 },
  { d: 200, elev: NaN }, { d: 300, elev: 160 },
];

<GradeProfile data={gappy} title="Partial track" />
```

A descent-only route has no climb to grade, so no pitch is emphasised and the summary reports **"600 m, no real
climb."** — climbing difficulty is the whole story, so descents always take the gentlest colour rather than borrowing a
climb's. A non-finite elevation breaks the profile into a gap: the segments touching it drop out and the ridge splits,
so a missing reading never invents a grade. A flat route reports the "no real climb" sentence too, and a single point
has no segment to grade at all, so its accessible name falls back to **"No data."**


## Why this default

Two decisions carry the chart. Grade is **quantized** into bins, not drawn as a continuous colour ramp — a route reads
as "gentle / rolling / steep / wall", categories a rider can act on, instead of a gradient nobody can decode at a
glance. And the default `bins` of `[3, 6, 10]` percent match how climbs are actually described, with the steepest pitch
labelled so the hardest moment is never buried. Below 72 pixels wide the four bins collapse to a simple
flat-versus-climb read, because the finer classes stop being separable there.

## Accessibility

The accessible name states the route's shape in words — **"900, 67 gain; steepest 16% at 800."** — distance, total
climb, and where the hardest pitch falls, none of it dependent on colour. The interactive entry announces each pitch as
you rove it (`←`/`→`), giving the true grade and the cumulative climb, so the encoding never has to be learned to be
used.

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) | `{ d: number; elev: number }[]` | Distance + elevation, monotonic in d, same unit so grade is a true percent. |
| `bins` | `[number, number, number]` | Ascending grade-% thresholds (always percent) that quantize the four difficulty bins. |
| `format` | `Intl.NumberFormatOptions \| (n) => string` | Formats distance and elevation in the summary and readout; grades always render as percent. |
| `label` | `"max" \| "none"` | Mark the steepest pitch, or render the profile alone. |
| `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).