---
title: time_weight() | Tiger Data Docs
description: Aggregate data into an intermediate time-weighted aggregate form for further calculation
---

Since [1.0.0](https://github.com/timescale/timescaledb-toolkit/releases/tag/1.0.0)

This is the first step for performing any time-weighted calculations. Use `time_weight` to create an intermediate aggregate (`TimeWeightSummary`) from your data. This intermediate form can then be used by one or more accessors in this group to compute final results.

Optionally, multiple such intermediate aggregate objects can be combined using [`rollup()`](/docs/reference/toolkit/time_weight/rollup/index.md) before an accessor is applied.

## Samples

Aggregate data from column `val` into daily time-weighted aggregates, using the linear interpolation method.

```
SELECT
    time_bucket('1 day'::interval, ts) as dt,
    time_weight('Linear', ts, val) AS tw
FROM foo
GROUP BY time_bucket('1 day'::interval, ts)
```

## Arguments

The syntax is:

```
time_weight(
    method TEXT,
    ts TIMESTAMPTZ,
    value DOUBLE PRECISION
) RETURNS TimeWeightSummary
```

| Name     | Type             | Default | Required | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| -------- | ---------------- | ------- | -------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `method` | TEXT             | -       | ✔        | The weighting method to use. The available methods are `linear` (or its alias `trapezoidal`, for those familiar with numeric integration methods) and `LOCF`, which stands for ‘last observation carried forward’. `linear` fills in missing data by interpolating linearly between the start and end points of the gap. `LOCF` fills in the gap by assuming that the value remains constant until the next value is seen. `LOCF` is most useful when a measurement is taken only when a value changes. `linear` is most useful if there are no such guarantees on the measurement. The method names are case-insensitive. |
| `ts`     | TIMESTAMPTZ      | -       | ✔        | The time at each point. Null values are ignored. An aggregate evaluated on only `null` values returns `null`.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| `value`  | DOUBLE PRECISION | -       | ✔        | The value at each point to use for the time-weighted aggregate. Null values are ignored. An aggregate evaluated on only `null` values returns `null`.                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |

## Returns

| Column       | Type              | Description                                                                                      |
| ------------ | ----------------- | ------------------------------------------------------------------------------------------------ |
| time\_weight | TimeWeightSummary | A `TimeWeightSummary` object that can be passed to other functions within the time-weighting API |