> For the complete documentation index, see [llms.txt](https://docs.rootcause.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rootcause.ai/more-details/applications/application-modules/aggregate.md).

# Aggregate

> Group by columns and compute measures.

Groups by `groupBy` and computes `measures` within each group. With no `groupBy` the whole frame is one group, which is how a single total is taken.

## At a glance

|                          |                        |
| ------------------------ | ---------------------- |
| Module type              | `Aggregate`            |
| Category                 | Primitives · Dataframe |
| Default tier             | `reactive`             |
| Runs on                  | `reactive`, `durable`  |
| Starts a flow            | no                     |
| Holds a body             | no                     |
| Keeps state between runs | no                     |
| Available in             | every application type |

## Parameters

### `groupBy`

`string[]` · required · defaults to `[]`

The grouping columns. Empty makes the whole frame one group.

### `measures`

`object[]` · required · defaults to `[]`

What to compute per group: a column, a function, and the name to write it under.

## Inputs

| Port   | Kind        | Required | Description                                                                                                                           |
| ------ | ----------- | -------- | ------------------------------------------------------------------------------------------------------------------------------------- |
| `on`   | `event`     | no       | Implicit on every module that does not itself start a flow: wire an event here to make this module the start of what that event runs. |
| `data` | `dataframe` | yes      | The frame to work on.                                                                                                                 |

## Outputs

| Port     | Kind        | Connects to           | Description                                                           |
| -------- | ----------- | --------------------- | --------------------------------------------------------------------- |
| `output` | `dataframe` | `dataframe`, `signal` | One row per group: the grouping columns, then one column per measure. |

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