---
title: asap_smooth() | Tiger Data Docs
description: Downsample a time series using the ASAP smoothing algorithm
---

Since [1.11.0](https://github.com/timescale/timescaledb-toolkit/releases/tag/1.11.0)

Downsample your data with the [ASAP smoothing algorithm](http://arxiv.org/pdf/1703.00983). This algorithm preserves the approximate shape and larger trends of the input data, while minimizing the local variance between points.

## Samples

This example uses a table called `metrics`, with columns for `date` and `reading`. The columns contain measurements that have been accumulated over a large interval of time. This example takes that data and provides a smoothed representation of approximately 10 points, but that still shows any anomalous readings:

```
SET TIME ZONE 'UTC';
CREATE TABLE metrics(date TIMESTAMPTZ, reading DOUBLE PRECISION);
INSERT INTO metrics
SELECT
    '2020-1-1 UTC'::timestamptz + make_interval(hours=>foo),
    (5 + 5 * sin(foo / 12.0 * PI()))
    FROM generate_series(1,168) foo;


SELECT * FROM unnest(
  (SELECT asap_smooth(date, reading, 8)
    FROM metrics)
);
```

```
time                    |        value
------------------------+---------------------
2020-01-01 01:00:00+00  | 5.3664814565722665
2020-01-01 21:00:00+00  |  5.949469264090644
2020-01-02 17:00:00+00  |  5.582987807518377
2020-01-03 13:00:00+00  |  4.633518543427733
2020-01-04 09:00:00+00  |  4.050530735909357
2020-01-05 05:00:00+00  |  4.417012192481623
2020-01-06 01:00:00+00  |  5.366481456572268
2020-01-06 21:00:00+00  |  5.949469264090643
```

## Arguments

The syntax is:

```
asap_smooth(
  ts TIMESTAMPTZ,
  value DOUBLE PRECISION,
  resolution INT
) RETURNS Timevector
```

| Name       | Type             | Default | Required | Description                                                                                              |
| ---------- | ---------------- | ------- | -------- | -------------------------------------------------------------------------------------------------------- |
| ts         | TIMESTAMPTZ      | -       | ✔        | Timestamps for each data point                                                                           |
| value      | DOUBLE PRECISION | -       | ✔        | The value at each timestamp                                                                              |
| resolution | INT              | -       | ✔        | The approximate number of points to return. Determines the horizontal resolution of the resulting graph. |

## Returns

| Column       | Type       | Description                                                                                                                                                                                                                             |
| ------------ | ---------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| asap\_smooth | Timevector | An object representing a series of values occurring at set intervals from a starting time. It can be unpacked with `unnest`. For more information, see the documentation on [timevectors](/docs/reference/toolkit/timevector/index.md). |