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danfo.merge

Merge DataFrame or named Series objects with a database-style join.The join is done on columns or indexes.

danfo.merge(options)

Parameters
Type
Description

options

Object

left: A DataFrame or named Series object.

right: Another DataFrame or named Series object.

on: Column names to join on. Must be found in both the left and right DataFrame and/or Series objects.

how: One of 'left','right','outer', 'inner'. Defaults to 'inner'

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Examples

danfo.js merge function is similar to Pandas merge and performs in-memory join operations idiomatically very similar to relational databases like SQL.

danfo.js provides a single function, merge(), as the entry point for all standard database join operations between DataFrame or named Series objects.

For a more intuitive understanding, this guidearrow-up-right on the Pandasarrow-up-right doc is worth reading.

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Merging by a single key found in both axis

In the following example, we perform an inner join. An inner join requires each row in the two joined DataFrames to have matching column values. This is similar to the intersection of two sets. It returns a DataFrame with only those rows that have common characteristics.

const dfd = require("danfojs-node")


let data = [['K0', 'k0', 'A0', 'B0'], ['k0', 'K1', 'A1', 'B1'],
            ['K1', 'K0', 'A2', 'B2'], ['K2', 'K2', 'A3', 'B3']]

let data2 = [['K0', 'k0', 'C0', 'D0'], ['K1', 'K0', 'C1', 'D1'],
            ['K1', 'K0', 'C2', 'D2'], ['K2', 'K0', 'C3', 'D3']]

let colum1 = ['Key1', 'Key2', 'A', 'B']
let colum2 = ['Key1', 'Key2', 'A', 'D']

let df1 = new dfd.DataFrame(data, { columns: colum1 })
let df2 = new dfd.DataFrame(data2, { columns: colum2 })
df1.print()
df2.print()

let merge_df = dfd.merge({ "left": df1, "right": df2, "on": ["Key1"], how: "inner"})
merge_df.print()

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Inner Join/Merge by multiple keys found in both axis

Merging by two keys takes into consideration the keys appearing in bothleft and right DataFrame.

The how parameter takes other types of joins like left, right and outer join and these are similar to their SQL equivalent

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Outer join/merge on DataFrame

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Left join/merge on DataFrame

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Right join/merge on DataFrame

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See also danfo.concat for joining objects based on axis.

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