> ## Documentation Index
> Fetch the complete documentation index at: https://docs.darvas.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Aggregators

> ta.highest, ta.lowest, ta.median, ta.mode, ta.change, ta.cum, ta.barssince - range and cumulative aggregation functions.

## `ta.highest(source, length)` - Highest value

Maximum of `source` over `length` bars.

```js theme={null}
onBar(() => {
  plot("52-week High", ta.highest(ctx.high, 365));
});
```

## `ta.lowest(source, length)` - Lowest value

Minimum of `source` over `length` bars.

```js theme={null}
onBar(() => {
  plot("20-bar Low", ta.lowest(ctx.low, 20));
});
```

## `ta.median(source, length)` - Median

Middle value when sorted over `length` bars.

```js theme={null}
onBar(() => {
  plot("Median close", ta.median(ctx.close, 20));
});
```

## `ta.mode(source, length)` - Most frequent value

Returns the value that appears most often in the window. Returns `NaN` if there is a tie.

```js theme={null}
onBar(() => {
  const m = ta.mode(ctx.close, 10);
  if (!na(m)) plot("Mode", m);
});
```

## `ta.change(source, length?)` - Bar-over-bar change

Current value minus the value `length` bars ago. `length` defaults to `1`.

```js theme={null}
onBar(() => {
  const dailyChange = ta.change(ctx.close);      // close - prev close
  const weeklyChange = ta.change(ctx.close, 5);  // close vs 5 bars ago
  plot("Daily change", dailyChange);
});
```

## `ta.barssince(key, condition)` - Bars since true

Returns the number of bars elapsed since `condition` was last true. Requires a **unique string key** to identify this aggregator's state across bars.

```js theme={null}
onBar(() => {
  const rsi = ta.rsi(ctx.close, 14);
  const bars = ta.barssince("rsi-ob", rsi > 70);
  plot("Bars since OB", bars);
});
```

<Note>
  The `key` must be unique per call site. If two different `ta.barssince` calls share the same key, they will interfere with each other's state. Use descriptive keys like `"rsi-crossover-14"` rather than `"x"`.
</Note>

## `ta.cum(key, value)` - Cumulative sum

Returns the running sum of `value` accumulated since the first bar. Requires a **unique string key**.

```js theme={null}
onBar(() => {
  const upVolume = ctx.close() > ctx.open() ? ctx.volume() : 0;
  const cumUpVol = ta.cum("up-volume", upVolume);
  plot("Cum up volume", cumUpVol);
});
```

## Stateful aggregator keys - budget impact

`ta.barssince` and `ta.cum` each consume one slot from the [64-Series budget](/reference/api-limits). Every unique key creates one internal Series. If you have many call sites, keep an eye on the Series count.

<Warning>
  Each unique `key` passed to `ta.barssince` or `ta.cum` allocates an internal Series. The total across explicit `Series()` calls and stateful aggregator keys must not exceed 64.
</Warning>

## Related pages

<CardGroup cols={2}>
  <Card title="Pivots" href="/ta/pivots">
    ta.pivothigh / ta.pivotlow - structural aggregators.
  </Card>

  <Card title="Series" href="/essentials/series">
    Manual Series storage for custom aggregation.
  </Card>

  <Card title="API limits" href="/reference/api-limits">
    64-Series budget shared with stateful aggregators.
  </Card>
</CardGroup>