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### Table of Contents

-   [GroupedDataFrame][1]
    -   [Parameters][2]
    -   [toCollection][3]
        -   [Examples][4]
    -   [show][5]
        -   [Parameters][6]
        -   [Examples][7]
    -   [listGroups][8]
        -   [Examples][9]
    -   [listHashs][10]
        -   [Examples][11]
    -   [map][12]
        -   [Parameters][13]
        -   [Examples][14]
    -   [filter][15]
        -   [Parameters][16]
        -   [Examples][17]
    -   [chain][18]
        -   [Parameters][19]
        -   [Examples][20]
    -   [aggregate][21]
        -   [Parameters][22]
        -   [Examples][23]
    -   [pivot][24]
        -   [Parameters][25]
        -   [Examples][26]
    -   [melt][27]
        -   [Parameters][28]
        -   [Examples][29]

## GroupedDataFrame

[src/group.js:6-239][30]

Grouped DataFrame structure grouping DataFrame rows by column value.

### Parameters

-   `df` **DataFrame** The DataFrame to group by.
-   `columnNames`  
-   `groups`  
-   `hashes`  
-   `columnName` **[String][31]** The column used for the group by.

### toCollection

[src/group.js:39-41][32]

Convert GroupedDataFrame into collection (Array) of dictionnaries (Object).

#### Examples

```javascript
groupedDF.toCollection();
```

Returns **[Array][33]** An Array containing group: {groupKey, group}.

### show

[src/group.js:50-60][34]

Display the GroupedDataFrame as String Table.

#### Parameters

-   `quiet` **[Boolean][35]** Quiet mode. If true, it doesn't trigger console.log(). (optional, default `false`)

#### Examples

```javascript
groupedDf.show()
```

Returns **[String][31]** The GroupedDataFrame as String Table.

### listGroups

[src/group.js:68-70][36]

List GroupedDataFrame groups.

#### Examples

```javascript
gdf.listGroups()
```

Returns **[Array][33]** An Array containing GroupedDataFrame group names.

### listHashs

[src/group.js:78-80][37]

List GroupedDataFrame groups as a hashCode.

#### Examples

```javascript
gdf.listHashCodes()
```

Returns **[Array][33]** An Array containing GroupedDataFrame hash codes.

### map

[src/group.js:89-95][38]

Map on DataFrame groups.

#### Parameters

-   `func` **[Function][39]** The function to apply to each row of each group.

#### Examples

```javascript
groupedDF.map((row,i) => row.set('b', row.get('a')*i));
```

Returns **DataFrame** A new DataFrame containing the result.

### filter

[src/group.js:104-114][40]

Filter a grouped DataFrame.

#### Parameters

-   `condition` **[Function][39]** A filter function or a column/value object.

#### Examples

```javascript
groupedDF.filter((row,i) => (i === 0));
```

Returns **DataFrame** A new filtered DataFrame.

### chain

[src/group.js:129-135][41]

Chain maps and filters functions on DataFrame by optimizing their executions.
If a function returns boolean, it's a filter. Else it's a map.
It can be 10 - 100 x faster than standard chains of .map() and .filter().

#### Parameters

-   `funcs` **...[Function][39]** Functions to apply on the DataFrame rows taking the row as parameter.

#### Examples

```javascript
groupedDF.chain(
     (row, i) => (i === 0), // filter
     row => row.set('column1', 3),  // map
     row => row.get('column2') === '5' // filter
)
```

Returns **DataFrame** A new DataFrame with modified rows.

### aggregate

[src/group.js:145-153][42]

Create an aggregation from a function.

#### Parameters

-   `func` **[Function][39]** The aggregation function.
-   `columnName` **[String][31]** The column name created by the aggregation. (optional, default `'aggregation'`)

#### Examples

```javascript
groupedDF.aggregate(group => group.stat.sum('column1'));
```

Returns **DataFrame** A new DataFrame with a column 'aggregation' containing the result.

### pivot

[src/group.js:163-191][43]

Pivot a GroupedDataFrame.

#### Parameters

-   `columnToPivot` **[String][31]** The column which will be transposed as columns.
-   `func` **[Function][39]** The function to define each column value from a DataFrame. (optional, default `(gdf)=>gdf.count()`)

#### Examples

```javascript
df.groupBy('carType').pivot('carModel', values => values.stat.sum('kms'))
```

Returns **DataFrame** The pivot DataFrame.

### melt

[src/group.js:201-238][44]

Melt a DataFrame to make it tidy. It's the reverse of GroupedDataFrame.pivot().

#### Parameters

-   `variableColumnName` **[String][31]** The column name containing values. (optional, default `'value'`)
-   `valueColumnName`   (optional, default `"value"`)

#### Examples

```javascript
df.groupBy('carType').melt('kms')
```

Returns **DataFrame** The tidy DataFrame.

[1]: #groupeddataframe

[2]: #parameters

[3]: #tocollection

[4]: #examples

[5]: #show

[6]: #parameters-1

[7]: #examples-1

[8]: #listgroups

[9]: #examples-2

[10]: #listhashs

[11]: #examples-3

[12]: #map

[13]: #parameters-2

[14]: #examples-4

[15]: #filter

[16]: #parameters-3

[17]: #examples-5

[18]: #chain

[19]: #parameters-4

[20]: #examples-6

[21]: #aggregate

[22]: #parameters-5

[23]: #examples-7

[24]: #pivot

[25]: #parameters-6

[26]: #examples-8

[27]: #melt

[28]: #parameters-7

[29]: #examples-9

[30]: https://github.com/Gmousse/dataframe-js/blob/add47391719e84537fdc30c80f762b3a8b38ba9a/src/group.js#L6-L239 "Source code on GitHub"

[31]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String

[32]: https://github.com/Gmousse/dataframe-js/blob/add47391719e84537fdc30c80f762b3a8b38ba9a/src/group.js#L39-L41 "Source code on GitHub"

[33]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array

[34]: https://github.com/Gmousse/dataframe-js/blob/add47391719e84537fdc30c80f762b3a8b38ba9a/src/group.js#L50-L60 "Source code on GitHub"

[35]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean

[36]: https://github.com/Gmousse/dataframe-js/blob/add47391719e84537fdc30c80f762b3a8b38ba9a/src/group.js#L68-L70 "Source code on GitHub"

[37]: https://github.com/Gmousse/dataframe-js/blob/add47391719e84537fdc30c80f762b3a8b38ba9a/src/group.js#L78-L80 "Source code on GitHub"

[38]: https://github.com/Gmousse/dataframe-js/blob/add47391719e84537fdc30c80f762b3a8b38ba9a/src/group.js#L89-L95 "Source code on GitHub"

[39]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function

[40]: https://github.com/Gmousse/dataframe-js/blob/add47391719e84537fdc30c80f762b3a8b38ba9a/src/group.js#L104-L114 "Source code on GitHub"

[41]: https://github.com/Gmousse/dataframe-js/blob/add47391719e84537fdc30c80f762b3a8b38ba9a/src/group.js#L129-L135 "Source code on GitHub"

[42]: https://github.com/Gmousse/dataframe-js/blob/add47391719e84537fdc30c80f762b3a8b38ba9a/src/group.js#L145-L153 "Source code on GitHub"

[43]: https://github.com/Gmousse/dataframe-js/blob/add47391719e84537fdc30c80f762b3a8b38ba9a/src/group.js#L163-L191 "Source code on GitHub"

[44]: https://github.com/Gmousse/dataframe-js/blob/add47391719e84537fdc30c80f762b3a8b38ba9a/src/group.js#L201-L238 "Source code on GitHub"