# ControlStrip (/docs/charts/control-strip)

Thirty fill-weight readings off a production line, two of them outside the band. ControlStrip separates ordinary process
variation from a genuine excursion: it is a Shewhart individuals chart, and the control band is the process center ± 3σ̂,
where **σ̂ = mean moving range ÷ 1.128** — the individuals estimator, stated outright (sample SD is not used; it inflates
the limits under drift). In-control points are bare vertices. Only out-of-control points are marked, ringed in the
negative color, so the eye lands on the exception instead of scanning every dot.

```tsx
import { ControlStrip } from "@microcharts/react/control-strip";

// 30 fill-weight readings (g); mostly in control, two excursions const weights = [ 74, 73, 75, 74, 76, 73, 74, 75, 74,
73, 82, 74, 75, 73, 74, 76, 74, 73, 75, 74, 66, 74, 75, 74, 73, 76, 74, 75, 74, 73, ];

<ControlStrip data={weights} title="Line 3 fill weight" />
```

## Install

```tsx
import { ControlStrip } from "@microcharts/react/control-strip";

<ControlStrip data={weights} title="Line 3 fill weight" />
```

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

## Try it

```tsx
import { ControlStrip } from "@microcharts/react/control-strip/interactive";

<ControlStrip
  data={weights}
/>
```

## When to use it

Use it for a production line or metric in a table cell, an SPC control chart in a KPI card, or flagging out-of-control
excursions. For a plain trend reach for Sparkline; for a strongly trending series, ChangePoint, since control limits
assume a stationary process.

## Sizing

**Western Electric run rules**

```tsx
<ControlStrip data={weights} rules="we" />
```

**known baseline (golden period)**

```tsx
<ControlStrip data={weights} baseline={74} />
```

## Variants

`rules="we"` adds the implemented Western Electric subset, enumerated so none of them fires silently: WE-1 (a point
beyond 3σ), WE-2 (two of three beyond 2σ), and WE-4 (eight on one side). `dots="all"` draws every point rather than only
the excursions, and `limits="percentile"` swaps the ±3σ̂ band for stated quantiles, for skewed processes.

```tsx
const weights = [
  74, 73, 75, 74, 76, 73, 74, 75, 74, 73, 82, 74, 75, 73, 74, 76, 74, 73, 75, 74, 66, 74, 75, 74,
  73, 76, 74, 75, 74, 73,
];

<ControlStrip data={weights} rules="we" />
<ControlStrip data={weights} dots="all" />
```

```tsx
<ControlStrip
  data={[2.4, 2.5, 2.45, 2.55, 2.5, 2.6, 2.4, 2.5, 2.45, 2.9, 2.5, 2.55]}
  format={{ maximumFractionDigits: 1 }}
  locale="de-DE"
/>
```

The chart draws no in-chart numbers, so `format`/`locale` shape the accessible summary and the interactive
announcements. The strip above reads "All 12 points within control limits (center 2,5, limits 2,1–2,9)." with German
decimal commas.

## Edge cases

```tsx
// the band gets a dashed outline and the summary appends
// "Limits provisional (n=6)"
<ControlStrip data={[10, 11, 9, 10, 12, 8]} />
```

```tsx
// MR̄ = 0 → σ̂ = 0: the band collapses into the center hairline
// instead of painting a fake zero-height zone
<ControlStrip data={[5, 5, 5, 5]} />
```

Below 10 points there are too few moving ranges to trust σ̂, so the band gets a dashed outline and the summary appends
"Limits provisional (n=6)". A constant series has MR̄ = 0 and therefore σ̂ = 0: the band collapses into the center
hairline rather than painting a fake zero-height zone.

## Four homes

**In a sentence**

```tsx
<p>
  Line 3 fill weight{" "}
  <span className="mc-inline">
    <ControlStrip data={weights} summary={false} />
  </span>{" "}
  — in control except one excursion at t=18.
</p>
```

**In a table cell**

```tsx
<td>
  <ControlStrip data={weights} />
</td>
```

**In a KPI card**

```tsx
<div className="kpi">
  <span className="figure">74g</span>
  <span className="unit">in control</span>
  <ControlStrip data={weights} />
</div>
```

**In a tab header**

```tsx
<button className="tab">
  Line 1 <ControlStrip data={weights} />
</button>
```

## Accessibility

The accessible name states the excursion count, the center, and the limits: **"2 of 30 points outside control limits
(center 74.17, limits 67.84–80.49)."** An in-control run reads "All N points within control limits …". The interactive
entry steps the points, and out-of-control points announce which limit they crossed.

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, press `Escape`, or
press outside the chart. On touch, a tap pins and a drag scrubs.

## Props

| Prop | Type | Description |
| --- | --- | --- |
| `data` (required) | `number[]` | Sequential measurements. |
| `limits` | `"sigma" \| "percentile"` | ±3σ̂ (default) or empirical p0.135/p99.865 for skewed processes. |
| `baseline` | `number` | Known process center from a reference period (else = mean). |
| `rules` | `"none" \| "we"` | Western Electric secondary run rules (WE-1/2/4 subset). |
| `dots` | `"out" \| "all" \| "none"` | Mark only out-of-control points (default), every point, or none. |
| `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).