> ## 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.

# intercept()

> Calculate the y-intercept from a counter aggregate

<Icon icon="tag" iconType="duotone" /> Since [1.3.0][toolkit-1.3.0]

Calculate the y-intercept of a linear least-squares fit between counter value and time. This corresponds to the
projected value at the Postgres epoch `(2000-01-01 00:00:00+00)`. You can use the y-intercept with the slope to plot a
best-fit line.

## Samples

Calculate the y-intercept of the linear fit for each 15-minute counter aggregate.

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

## Arguments

The syntax is:

```sql theme={"dark"}
intercept(
    summary CounterSummary
) RETURNS DOUBLE PRECISION
```

| Name      | Type             | Default | Required | Description                                                    |
| --------- | ---------------- | ------- | -------- | -------------------------------------------------------------- |
| `summary` | `CounterSummary` | -       | ✔        | A counter aggregate created using [`counter_agg`][counter-agg] |

## Returns

| Column    | Type             | Description                                     |
| --------- | ---------------- | ----------------------------------------------- |
| intercept | DOUBLE PRECISION | The y-intercept of the linear least-squares fit |

[counter-agg]: /api-reference/timescaledb-toolkit/counters-and-gauges/counter_agg/counter_agg

[toolkit-1.3.0]: https://github.com/timescale/timescaledb-toolkit/releases/tag/1.3.0