---
title: intercept() | Tiger Data Docs
description: Calculate the y-intercept from a gauge aggregate
---

Early access [1.6.0](https://github.com/timescale/timescaledb-toolkit/releases/tag/1.6.0)

Calculate the y-intercept of a linear least-squares fit between gauge value and time. This corresponds to the projected value at the PostgreSQL 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 gauge aggregate.

```
SELECT
    id,
    bucket,
    intercept(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:

```
intercept(
    summary GaugeSummary
) RETURNS DOUBLE PRECISION
```

| Name      | Type           | Default | Required | Description                                                                                                             |
| --------- | -------------- | ------- | -------- | ----------------------------------------------------------------------------------------------------------------------- |
| `summary` | `GaugeSummary` | -       | ✔        | A gauge aggregate created using [`gauge_agg`](/docs/reference/toolkit/counters-and-gauges/gauge_agg/gauge_agg/index.md) |

## Returns

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