danfo.dataframe.groupby.md

description
Group DataFrame using a mapper or by a Series of columns.

DataFrame.groupby

danfo.DataFrame.groupby(columns)

Parameters	Type	Description	Default
columns	Array	The names of a column(s) in the DataFrame to group by

Examples

Groupby a single column from a DataFrame

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

const dfd = require("danfojs-node")

let data = [["Pear", 2, 3], ["Pear", 5, 6], ["Apple", 30, 40], ["Apple", 89, 78]]
let cols = ["A", "B", "C"]

let df = new dfd.DataFrame(data, { columns: cols })
let group_df = df.groupby(["A"])
console.log(group_df)

// ouput
Groupby {
  colDict: {
    Pear: { A: [Array], B: [Array], C: [Array] },
    Apple: { A: [Array], B: [Array], C: [Array] }
  },
  keyToValue: { Pear: [ 'Pear' ], Apple: [ 'Apple' ] },
  keyCol: [ 'A' ],
  data: [
    [ 'Pear', 2, 3 ],
    [ 'Pear', 5, 6 ],
    [ 'Apple', 30, 40 ],
    [ 'Apple', 89, 78 ]
  ],
  columnName: [ 'A', 'B', 'C' ],
  colDtype: [ 'string' ],
  colIndex: [ 0 ]
}

{% endtab %}

{% tab title="Browser" %}

{% endtab %} {% endtabs %}

A groupby operation will return a GroupBy class object. You can apply any of the following operation on the groupby result:

1. count
2. sum
3. std
4. var
5. mean
6. cumSum
7. cumMax
8. cumProd
9. cummin
10. max
11. min

Example of Groupby and apply a sum function

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

const dfd = require("danfojs-node")

let data = [["Pear", 2, 3], ["Pear", 5, 6], ["Apple", 30, 40], ["Apple", 89, 78]]
let cols = ["A", "B", "C"]
let df = new dfd.DataFrame(data, { columns: cols })
let group_df = df.groupby(["A"]).sum()

group_df.print()

{% endtab %} {% endtabs %}

╔════════════╤═══════════════════╤═══════════════════╤═══════════════════╗
║            │ A                 │ B_sum             │ C_sum             ║
╟────────────┼───────────────────┼───────────────────┼───────────────────╢
║ 0          │ Pear              │ 7                 │ 9                 ║
╟────────────┼───────────────────┼───────────────────┼───────────────────╢
║ 1          │ Apple             │ 119               │ 118               ║
╚════════════╧═══════════════════╧═══════════════════╧═══════════════════╝

Groupby a two columns from a DataFrame

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

const dfd = require("danfojs-node")

let data = [["Pear", 2, 3], ["Pear", 2, 6], ["Apple", 30, 40], ["Apple", 89, 78]]
let cols = ["A", "B", "C"]
let df = new dfd.DataFrame(data, { columns: cols })
let group_df = df.groupby(["A", "B"]).sum()

group_df.print()

{% endtab %}

{% tab title="Browser" %}

{% endtab %} {% endtabs %}

╔════════════╤═══════════════════╤═══════════════════╤═══════════════════╗
║            │ A                 │ B                 │ C_sum             ║
╟────────────┼───────────────────┼───────────────────┼───────────────────╢
║ 0          │ Pear              │ 2                 │ 9                 ║
╟────────────┼───────────────────┼───────────────────┼───────────────────╢
║ 1          │ Apple             │ 30                │ 40                ║
╟────────────┼───────────────────┼───────────────────┼───────────────────╢
║ 2          │ Apple             │ 89                │ 78                ║
╚════════════╧═══════════════════╧═══════════════════╧═══════════════════╝