> For the complete documentation index, see [llms.txt](https://danfo.jsdata.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://danfo.jsdata.org/api-reference/groupby/groupby.mean.md).

# Groupby.mean

> danfo.Series.mean() \[[source](https://github.com/javascriptdata/danfojs/blob/0d33e344b80a3ed54c91c9393ac3b583d4b0b1a4/src/danfojs-base/aggregators/groupby.ts#L464)]

**Parameters**: None

**Return**: DataFrame

**Examples**

Obtain the mean of a column for each group, group by one column

{% tabs %}
{% tab title="Node" %}

```javascript
const dfd = require("danfojs-node")

let data ={A: ['foo', 'bar', 'foo', 'bar',
                'foo', 'bar', 'foo', 'foo'],
           B: ['one', 'one', 'two', 'three',
                'two', 'two', 'one', 'three'],
           C: [1,3,2,4,5,2,6,7],
           D: [3,2,4,1,5,6,7,8]
}

let df = new dfd.DataFrame(data)


let grp = df.groupby(["A"])
grp.col(["C"]).mean().print()
```

{% endtab %}
{% endtabs %}

```
  Shape: (2,2) 

╔═══╤═══════════════════╤═══════════════════╗
║   │ A                 │ C_mean            ║
╟───┼───────────────────┼───────────────────╢
║ 0 │ foo               │ 4.19999980926...  ║
╟───┼───────────────────┼───────────────────╢
║ 1 │ bar               │ 3                 ║
╚═══╧═══════════════════╧═══════════════════╝
```

Obtain the mean for two columns for each group, group by one column

{% tabs %}
{% tab title="Node" %}

```javascript
const dfd = require("danfojs-node")


let data ={A: ['foo', 'bar', 'foo', 'bar',
                'foo', 'bar', 'foo', 'foo'],
           B: ['one', 'one', 'two', 'three',
                'two', 'two', 'one', 'three'],
           C: [1,3,2,4,5,2,6,7],
           D: [3,2,4,1,5,6,7,8]
}

let df = new dfd.DataFrame(data)


let grp = df.groupby(["A"])
grp.col(["C","D"]).mean().print()
```

{% endtab %}
{% endtabs %}

```
 Shape: (2,3) 

╔═══╤═══════════════════╤═══════════════════╤═══════════════════╗
║   │ A                 │ C_mean            │ D_mean            ║
╟───┼───────────────────┼───────────────────┼───────────────────╢
║ 0 │ foo               │ 4.19999980926...  │ 5.40000009536...  ║
╟───┼───────────────────┼───────────────────┼───────────────────╢
║ 1 │ bar               │ 3                 │ 3                 ║
╚═══╧═══════════════════╧═══════════════════╧═══════════════════╝
```

Obtain the mean for a column for each group, group by two columns

{% tabs %}
{% tab title="Node" %}

```javascript
const dfd = require("danfojs-node")

let data ={A: ['foo', 'bar', 'foo', 'bar',
                'foo', 'bar', 'foo', 'foo'],
           B: ['one', 'one', 'two', 'three',
                'two', 'two', 'one', 'three'],
           C: [1,3,2,4,5,2,6,7],
           D: [3,2,4,1,5,6,7,8]
}

let df = new dfd.DataFrame(data)


let grp = df.groupby(["A","B"])
grp.col(["C"]).mean().print()
```

{% endtab %}
{% endtabs %}

```
    Shape: (5,3) 

╔═══╤═══════════════════╤═══════════════════╤═══════════════════╗
║   │ A                 │ B                 │ C_mean            ║
╟───┼───────────────────┼───────────────────┼───────────────────╢
║ 0 │ foo               │ one               │ 3.5               ║
╟───┼───────────────────┼───────────────────┼───────────────────╢
║ 1 │ foo               │ two               │ 3.5               ║
╟───┼───────────────────┼───────────────────┼───────────────────╢
║ 2 │ foo               │ three             │ 7                 ║
╟───┼───────────────────┼───────────────────┼───────────────────╢
║ 3 │ bar               │ one               │ 3                 ║
╟───┼───────────────────┼───────────────────┼───────────────────╢
║ 4 │ bar               │ two               │ 2                 ║
╚═══╧═══════════════════╧═══════════════════╧═══════════════════╝
```

Obtain the mean for two columns for each group, group by two columns

{% tabs %}
{% tab title="Node" %}

```javascript
const dfd = require("danfojs-node")

let data ={A: ['foo', 'bar', 'foo', 'bar',
                'foo', 'bar', 'foo', 'foo'],
           B: ['one', 'one', 'two', 'three',
                'two', 'two', 'one', 'three'],
           C: [1,3,2,4,5,2,6,7],
           D: [3,2,4,1,5,6,7,8]
}

let df = new dfd.DataFrame(data)
let grp = df.groupby(["A","B"])
grp.col(["C","D"]).mean().print()
```

{% endtab %}
{% endtabs %}

```
    Shape: (5,4) 

╔═══╤═══════════════════╤═══════════════════╤═══════════════════╤═══════════════════╗
║   │ A                 │ B                 │ C_mean            │ D_mean            ║
╟───┼───────────────────┼───────────────────┼───────────────────┼───────────────────╢
║ 0 │ foo               │ one               │ 3.5               │ 5                 ║
╟───┼───────────────────┼───────────────────┼───────────────────┼───────────────────╢
║ 1 │ foo               │ two               │ 3.5               │ 4.5               ║
╟───┼───────────────────┼───────────────────┼───────────────────┼───────────────────╢
║ 2 │ foo               │ three             │ 7                 │ 8                 ║
╟───┼───────────────────┼───────────────────┼───────────────────┼───────────────────╢
║ 3 │ bar               │ one               │ 3                 │ 2                 ║
╟───┼───────────────────┼───────────────────┼───────────────────┼───────────────────╢
║ 4 │ bar               │ two               │ 2                 │ 6                 ║
╚═══╧═══════════════════╧═══════════════════╧═══════════════════╧═══════════════════╝
```

***