# RetentionCurve (/docs/charts/retention-curve)

A cohort has run twelve weeks and the curve looks like it is flattening. RetentionCurve draws it as a **step** line
(cohort periods are discrete) on a scale **locked to 0–100%**: the full range is the frame a share is read against, and
a truncated floor would exaggerate or hide the drop. When the curve flattens, a dotted plateau marker appears. A
`compare` series rides behind as a subordinate dashed ghost.

```tsx
import { RetentionCurve } from "@microcharts/react/retention-curve";

<RetentionCurve
  data={[1, 0.72, 0.55, 0.47, 0.42, 0.4, 0.39, 0.385, 0.382, 0.38, 0.379, 0.378]}
  unit="week"
  title="W12 cohort"
/>
```

## Install

```tsx
import { RetentionCurve } from "@microcharts/react/retention-curve";

<RetentionCurve data={cohort} unit="week" title="W12 cohort" />
```

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 { RetentionCurve } from "@microcharts/react/retention-curve/interactive";

<RetentionCurve
  data={cohort}
  compare={industry}
/>
```

## When to use it

Use it for a cohort retention curve in a KPI card, your decay against an industry benchmark, and spotting whether
retention plateaus or keeps leaking. For a continuous signal use Sparkline; for one-number retention use Progress or
Delta.

## Sizing

**vs industry benchmark**

```tsx
<RetentionCurve data={cohort} compare={industry} />
```

**smooth (editorial)**

```tsx
// step is the honest default for cohort data
<RetentionCurve data={cohort} curve="smooth" />
```

## Variants

```tsx
<RetentionCurve
  data={[1, 0.72, 0.55, 0.47, 0.42, 0.4, 0.39, 0.385, 0.382, 0.38]}
  compare={[1, 0.6, 0.44, 0.37, 0.33, 0.3, 0.29, 0.285, 0.282, 0.28]}
/>
<RetentionCurve
  data={[1, 0.72, 0.55, 0.47, 0.42, 0.4, 0.39, 0.385, 0.382, 0.38]}
  curve="smooth"
/>
```

The compare series stays a dashed ghost behind your curve rather than a second competing line. `curve="smooth"`
interpolates between periods, which implies values that were never measured; the step default doesn't. The plateau
marker appears only when the mean period-over-period change across the tail falls below half a point, never as
decoration.

## Edge cases

```tsx
<RetentionCurve data={[1]} unit="week" />
```

```tsx
// values over 1.001 are auto-detected as percent, not fraction — same curve
<RetentionCurve data={[100, 72, 55, 47, 42, 40, 39]} unit="week" />
```

```tsx
<RetentionCurve
  data={[1, 0.72, 0.55, 0.47, 0.42, 0.4, 0.39]}
  unit="week"
  label="last"
  locale="de-DE"
/>
```

A single period is too short for plateau detection (the window needs at least four finite points) and renders as a
single step with no visible line. `data` accepts either a 0–1 fraction or a 0–100 percent series, whichever the max
value implies, so a raw percent export renders identically to its fraction form without a manual divide. With a
`locale`, the percent label and every announced number follow that locale's own formatting.

## Four homes

**In a sentence**

```tsx
<p>
  W12 cohort retention{" "}
  <span className="mc-inline">
    <RetentionCurve data={cohort} summary={false} />
  </span>{" "}
  — 38% at week 12, above benchmark.
</p>
```

**In a table cell**

```tsx
<td>
  <RetentionCurve data={cohort} />
</td>
```

**In a KPI card**

```tsx
<div className="kpi">
  <span className="figure">38%</span>
  <span className="unit">retained</span>
  <RetentionCurve data={cohort} />
</div>
```

**In a tab header**

```tsx
<button className="tab">
  Jan <RetentionCurve data={cohort} />
</button>
```

## Accessibility

The accessible name states the final retention and, when one is detected, the plateau: **"38% retained after 10 weeks;
curve plateaus from week 6."** The interactive entry steps the periods and announces each period's retention alongside
the benchmark's.

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[]` | Fraction retained per period (0–1 or 0–100); period 0 is typically 1.0. |
| `compare` | `number[]` | Peer/industry curve, drawn as a subordinate dashed ghost. The catalog word for a second series to read the first against (DualSparkline, StarSpoke). |
| `benchmark` | `number[]` | Deprecated alias for `compare`, still accepted and still winning when both are passed. |
| `plateau` | `boolean` | Detect + mark a plateau (default true). |
| `curve` | `"step" \| "smooth"` | Step (default — cohorts are discrete) or smooth (editorial). |
| `unit` | `string` | Period noun for the summary (default 'period'). |
| `label` | `"last" \| "none"` | Final retention in a right gutter. |
| `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).