> For the complete documentation index, see [llms.txt](https://docs.carto.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.carto.com/data-and-analysis/analytics-toolbox-for-bigquery/sql-reference/clustering.md).
# clustering
This module contains functions that perform clustering on geographies.
## ST\_CLUSTERKMEANS
```sql
ST_CLUSTERKMEANS(geog, numberOfClusters)
```
**Description**
Takes a set of points as input and partitions them into clusters using the k-means algorithm. Returns an array of tuples with the cluster index for each of the input features and the input geometry.
**Input parameters**
* `geog`: `ARRAY` points to be clustered.
* `numberOfClusters`: `INT64`|`NULL` numberOfClusters that will be generated. If `NULL` the default value `Math.sqrt(/2)` is used. The output number of cluster cannot be greater to the number of distinct points of the `geog`.
**Return type**
`ARRAY>`
**Example**
{% tabs %}
{% tab title="carto-un" %}
```sql
SELECT `carto-un`.carto.ST_CLUSTERKMEANS([ST_GEOGPOINT(0, 0), ST_GEOGPOINT(0, 1), ST_GEOGPOINT(5, 0), ST_GEOGPOINT(1, 0)], 2);
-- {cluster: 1, geom: POINT(0 0)}
-- {cluster: 1, geom: POINT(0 1)}
-- {cluster: 0, geom: POINT(5 0)}
-- {cluster: 1, geom: POINT(1 0)}
```
{% endtab %}
{% tab title="carto-un-eu" %}
```sql
SELECT `carto-un-eu`.carto.ST_CLUSTERKMEANS([ST_GEOGPOINT(0, 0), ST_GEOGPOINT(0, 1), ST_GEOGPOINT(5, 0), ST_GEOGPOINT(1, 0)], 2);
-- {cluster: 1, geom: POINT(0 0)}
-- {cluster: 1, geom: POINT(0 1)}
-- {cluster: 0, geom: POINT(5 0)}
-- {cluster: 1, geom: POINT(1 0)}
```
{% endtab %}
{% tab title="manual" %}
```sql
SELECT carto.ST_CLUSTERKMEANS([ST_GEOGPOINT(0, 0), ST_GEOGPOINT(0, 1), ST_GEOGPOINT(5, 0), ST_GEOGPOINT(1, 0)], 2);
-- {cluster: 1, geom: POINT(0 0)}
-- {cluster: 1, geom: POINT(0 1)}
-- {cluster: 0, geom: POINT(5 0)}
-- {cluster: 1, geom: POINT(1 0)}
```
{% endtab %}
{% endtabs %}
{% hint style="info" %}
**Additional examples**
* [New police stations based on Chicago crime location clusters](https://academy.carto.com/advanced-spatial-analytics/spatial-analytics-for-bigquery/step-by-step-tutorials/new-police-stations-based-on-chicago-crime-location-clusters)
{% endhint %}
This project has received funding from the [European Union’s Horizon 2020](https://ec.europa.eu/programmes/horizon2020/en) research and innovation programme under grant agreement No 960401.
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