Nest Your Data

In Dataprep by Trifacta, you can nest columns into arrays and objects (maps) using a variety of transformations.

Nested data types include the following types of data:

Arrays are lists of values, grouped into a single value. Examples:
```
[1,2,3,4]
```
```
[1,2,[a,b],4]
```

Objects are collections of key-value pairs. Examples:

{"make":"Subaru","model":"Outback","year":"2015","color":"black"}

{"make":"Subaru","model":"Outback","year":{"first":"2015","last":"2021"},"color":"black"}

In the above examples:

The first example is a flat or unnested Array or Object.
The first example is a nested Array or Object.

Nest Columns into Array

This section provides simple examples of nesting columns into Arrays by extracting values from a column or nesting one or more columns into an Array column.

Create by extraction:

You can create an array of values by extracting pattern-based values from a specified column. The following transformation extracts from the msg column a list of all values where all letters are capitalized and places them into the new acronyms column:

Transformation Name	`Extract matches into Array`
Parameter: Column	msg
Parameter: Pattern matching elements in the list	`{upper}+`
Parameter: New column name	acronyms

msg	acronyms
SCUBA, IMHO, is the greatest sport in the world.	["SCUBA","IMHO"]
	[]
LOL, that assignment you finished is DOA. You need to fix it PDQ.	["LOL","DOA","Y","PDQ"]

Notes:

An empty input column value renders an empty array.
In the final row, the Wrangle matches on the "Y" value. To fix this, you can change the Pattern matching value to the following, which matches on two or more uppercase letters in a row:
```
`{upper}{upper}+`
```

Create by nesting:

You can create arrays by nesting together the values from multiple columns:

num1	num2	num3
11	12	13
14	15	16
17	18	19

You can nest the values in num1 and num2 into a single array and then to nest the array with num3:

Note

If you are nesting a multi-level array, you should nest from the lowest level to the top level.

Transformation Name	`Nest columns into Objects`
Parameter: Columns1	num1
Parameter: Columns2	num2
Parameter: Nest columns to	Array
Parameter: New column name	nest1

Then, you can perform the nesting of the top-level elements:

Note

The order in which you list the columns to nest determines the order in which the elements appear in the generated array.

Transformation Name	`Nest columns into Objects`
Parameter: Columns1	nest1
Parameter: Columns2	num3
Parameter: Nest columns to	Array
Parameter: New column name	nest2

In the generated columns, you notice that all values are quoted, even though these values are integers.

Note

Elements that are generated into arrays using a nest transformation are always rendered as quoted values.

You can use the following transformation to remove the quotes from the nest2 column:

Transformation Name	`Replace text or patterns`
Parameter: Column	nest2
Parameter: Find	'"'
Parameter: Replace	(empty)
Parameter: Match all occurrences	true

num1	num2	num3	nest2
11	12	13	[[11,12],13]
14	15	16	[[14,15],16]
17	18	19	[[17,18],19]

Nest Columns into Objects

You can nest multiple columns into a single column of objects using nest transform.

This section provides a simple example of nesting columns into a new column of Object data type.

Source:

In the following example, furniture product dimensions are stored in separate columns in cm.

Category	Name	Length_cm	Width_cm	Height_cm
bench	Hooska	118.11	74.93	46.34
lamp	Tansk	30.48	30.48	165.1
bookshelf	Brock	27.94	160.02	201.93
couch	Loafy	95	227	83

Transformation:

Use the nest transform to bundle the data into a single column.

Transformation Name	`Nest columns into Objects`
Parameter: Columns	Length_cm,Width_cm,Height_cm
Parameter: Nest columns to	Object
Parameter: New column name	'Dimensions'

Results:

Category	Name	Length_cm	Width_cm	Height_cm	Dimensions
bench	Hooska	118.11	74.93	46.34	{"Length_cm":"118.11","Width_cm":"74.93","Height_cm":"46.34"}
lamp	Tansk	30.48	30.48	165.1	{"Length_cm":"30.48","Width_cm":"30.48","Height_cm":"165.1"}
bookshelf	Brock	27.94	160.02	201.93	{"Length_cm":"27.94","Width_cm":"160.02","Height_cm":"201.93"}
couch	Loafy	95	227	83	{"Length_cm":"95,"Width_cm":"227","Height_cm":"83"}

Hybrids of Arrays and Objects

A single Array or Object can contain other Arrays, Objects, or both. In fact, this structuring is essentially the JSON file format. In this example, you can see how data, when laid out in a single table, can be assembled into a set of JSON records. See EXAMPLE - Nest JSON Records.

In this section:

Nest Your Data

Nest Columns into Array

Nest Columns into Objects

Hybrids of Arrays and Objects

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