> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify-poc.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# irate_left()

> Calculate the instantaneous rate of change at the left, or earliest, edge of a gauge aggregate

<Icon icon="flask" /> Early access <Icon icon="tag" iconType="duotone" /> Since [1.6.0][toolkit-1.6.0]

Calculate the instantaneous rate of change at the left, or earliest, edge of a gauge aggregate. This is equal to the
second value minus the first value, divided by the time lapse between the two points. This calculation is useful for
fast-moving gauges.

## Samples

Get the instantaneous rate of change at the start of each 15-minute gauge aggregate.

```sql theme={"dark"}
SELECT
    id,
    bucket,
    irate_left(summary)
FROM (
    SELECT
        id,
        time_bucket('15 min'::interval, ts) AS bucket,
        gauge_agg(ts, val) AS summary
    FROM foo
    GROUP BY id, time_bucket('15 min'::interval, ts)
) t
```

## Arguments

The syntax is:

```sql theme={"dark"}
irate_left(
  summary GaugeSummary
) RETURNS DOUBLE PRECISION
```

| Name      | Type           | Default | Required | Description                                              |
| --------- | -------------- | ------- | -------- | -------------------------------------------------------- |
| `summary` | `GaugeSummary` | -       | ✔        | A gauge aggregate created using [`gauge_agg`][gauge-agg] |

## Returns

| Column      | Type             | Description                                                                            |
| ----------- | ---------------- | -------------------------------------------------------------------------------------- |
| irate\_left | DOUBLE PRECISION | The instantaneous rate of change at the left, or earliest, edge of the gauge aggregate |

[gauge-agg]: /api-reference/timescaledb-toolkit/counters-and-gauges/gauge_agg/gauge_agg

[toolkit-1.6.0]: https://github.com/timescale/timescaledb-toolkit/releases/tag/1.6.0