# Accumulation

{% hint style="info" %}
Check out the [accumulation tests](https://github.com/larswaechter/voici.js/tree/main/tests/body/accumulation) for more examples.
{% endhint %}

Accumulation allows you to calculate a value based on all the cells inside a given column. Therefore, you can pick one of the predefined [accumulation functions](https://voici.larswaechter.dev/reference/api-reference/accumulationfunction). For example:

* SUM
* MEAN
* MAX
* VARIANCE
* ...

{% hint style="warning" %}
The values `null` and `undefined` are excluded from accumulation.
{% endhint %}

Using the `accumulation` options you can provide the accumulated `columns`, a `bgColor` and a line `separator`. Inside `columns` provide the desired column you'd like to accumulate and the `AccumulationFunction` to apply.

```javascript
import { Table, AccumulationFunction } from 'voici.js'

const data = [
  { firstname: 'Homer', lastname: 'Simpson', age: 39 },
  { firstname: 'Marge', lastname: 'Simpson', age: 36 },
  { firstname: 'Bart', lastname: 'Simpson', age: 10 },
  { firstname: 'Lisa', lastname: 'Simpson', age: 8 },
  { firstname: 'Maggie', lastname: 'Simpson', age: 1 }
];

const config = {
  body: {
    accumulation: {
      separator: '-',
      columns: [
        {
          'age': AccumulationFunction.MEAN
        }
      ]
    }
  }
};

const table = new Table(data, config);
table.printPlain();
```

The accumulated output:

```
  firstname    lastname    age     
===================================
  Homer        Simpson     39      
  Marge        Simpson     36      
  Bart         Simpson     10      
  Lisa         Simpson     8       
  Maggie       Simpson     1       
-----------------------------------
                           18.800  
```

{% hint style="info" %}
You can also use accumulated values for [dynamic columns](https://voici.larswaechter.dev/examples/columns/dynamic-columns).
{% endhint %}


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://voici.larswaechter.dev/examples/accumulation.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.