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An array is a bracket set of commadelimited values. The following are valid arrays:
[1,2,3] ["A","B"] ["C",["D","E"],"F",["G",["H","I"]]]
Ragged arrays: If the number of elements varies between two arrays, they are considered ragged. In the above, all three arrays have a different number of toplevel elements (3,2,4).
Nested arrays: When an array element is an array itself, the element is considered a nested array. See the last example above.
Source Arrays
To be recognized as an array, a source column must contain values that are:
 Bracketed by square brackets
 Values in cell are delimited by commas
Such columns are likely to be recognized as Array data type.
For more information, see Array Data Type.
Create Arrays
Within Trifacta® Wrangler, you can generate arrays using values from one or more columns to do so.
Create by extraction
You can create an array of values by extracting patternbased 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 Trifacta pattern 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.
Source:
num1  num2  num3 

11  12  13 
14  15  16 
17  18  19 
You want to 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 multilevel 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 toplevel 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 
After removing the unused nest1
column, the data looks like the following:
num1  num2  num3  nest2 

11  12  13  [[11,12],13] 
14  15  16  [[14,15],16] 
17  18  19  [[17,18],19] 
Create from column values
You can use one of several available functions to create arrays from a column's values.
Source:
listVals 

5 
TRUE 
{"key1":"value1","keys2":"value2"} 
[1,2,3] 
My String 
5.5 
The following transformation generates a new column in which each row contains an array of all of the values of the input column:
Transformation Name  New formula 

Parameter: Formula type  Single row formula 
Parameter: Formula  LIST(listVals,1000) 
Parameter: New column name  listOfListVals 
Results:
listVals  listOfListVals 

5  ["5","TRUE","{\"key1\":\"value1\",\"keys2\":\"value2\"}","[1,2,3]","My String","5.5"] 
TRUE  ["5","TRUE","{\"key1\":\"value1\",\"keys2\":\"value2\"}","[1,2,3]","My String","5.5"] 
{"key1":"value1","keys2":"value2"}  ["5","TRUE","{\"key1\":\"value1\",\"keys2\":\"value2\"}","[1,2,3]","My String","5.5"] 
[1,2,3]  ["5","TRUE","{\"key1\":\"value1\",\"keys2\":\"value2\"}","[1,2,3]","My String","5.5"] 
My String  ["5","TRUE","{\"key1\":\"value1\",\"keys2\":\"value2\"}","[1,2,3]","My String","5.5"] 
5.5  ["5","TRUE","{\"key1\":\"value1\",\"keys2\":\"value2\"}","[1,2,3]","My String","5.5"] 
Notes:
 The second parameter on the LIST function defines the maximum number of values to write.
1000
is the default.  All values in the generated array are written as String values.
 Quoted values are escaped in the output.
The following functions allow you to generate various types of arrays from a column's set of values.
Function  Description 

LIST Function  Extracts the set of values from a column into an array stored in a new column. This function is typically part of an aggregation. 
UNIQUE Function 

LISTIF Function  Returns list of all values in a column for rows that match a specified condition. 
ROLLINGLIST Function  Computes the rolling list of values forward or backward of the current row within the specified column and returns an array of these values. 
RANGE Function  Computes an array of integers, from a beginning integer to an end (stop) integer, stepping by a third parameter. NOTE: The lower bound of the range is included, while the upper bound is not. 
Tip: Additional examples are available in the above links for these functions.
Create from Object type
You can extract the keys of an Object column into an array of string values. In an Object type, the values are listed in quoted key/value pairs and can be nested. See Object Data Type.
Source:
Suppose your Object data looks like the following:
myObject 

{"key1":"value1","key2":"value2","key3":"value3"} 
{"apples":"2","oranges":"4"} 
{"planes":{"boeing":"5","airbus":"4"},"trains":{"amtrak":"1","SP":"2"}, "automobiles":{"toyota":"100","nissan":"50"}} 
You can run the following transformation to extract the toplevel keys into arrays in a new named column:
NOTE: The KEYS function retrieves only the toplevel keys from the Object.
Transformation Name  New formula 

Parameter: Formula type  Single row formula 
Parameter: Formula  KEYS(myObject) 
Parameter: New column name  myObjectKeys 
Results:
myObject  myObjectKeys 

{"key1":"value1","key2":"value2","key3":"value3"}  ["key1","key2","key3"] 
{"apples":"2","oranges":"4"}  ["apples","oranges"] 
{"planes":{"boeing":"5","airbus":"4"},"trains":{"amtrak":"1","SP":"2"}, "automobiles":{"toyota":"100","nissan":"50"}}  ["planes","trains","automobiles"] 
For more information, see KEYS Function.
Read from Arrays
You can read values from arrays in your dataset.
NOTE: After an array has been created, you can append to the array or otherwise combine it with another array. You cannot replace values in the array without breaking apart the array and rebuilding it.
Function  Description 

IN Function 
Returns 
ARRAYELEMENTAT Function  Computes the 0based index value for an array element in the specified column, array literal, or function that returns an array. 
ARRAYLEN Function  Computes the number of elements in the arrays in the specified column, array literal, or function that returns an array. 
ARRAYUNIQUE Function  Generates an array of all unique elements among one or more arrays. 
Tip: Additional examples are available in the above links for these functions.
Compute from Arrays
You can use the following functions to perform computations on the values in your arrays:
Function  Description 

LISTSUM Function  Computes the sum of all numeric values found in input array. Input can be an array literal, a column of arrays, or a function returning an array. Input values must be of Integer or Decimal type. 
LISTMAX Function  Computes the maximum of all numeric values found in input array. Input can be an array literal, a column of arrays, or a function returning an array. Input values must be of Integer or Decimal type. 
LISTMIN Function  Computes the minimum of all numeric values found in input array. Input can be an array literal, a column of arrays, or a function returning an array. Input values must be of Integer or Decimal type. 
LISTAVERAGE Function  Computes the average of all numeric values found in input array. Input can be an array literal, a column of arrays, or a function returning an array. Input values must be of Integer or Decimal type. 
LISTVAR Function  Computes the variance of all numeric values found in input array. Input can be an array literal, a column of arrays, or a function returning an array. Input values must be of Integer or Decimal type. 
LISTSTDEV Function  Computes the standard deviation of all numeric values found in input array. Input can be an array literal, a column of arrays, or a function returning an array. Input values must be of Integer or Decimal type. 
LISTMODE Function  Computes the most common value of all numeric values found in input array. Input can be an array literal, a column of arrays, or a function returning an array. Input values must be of Integer or Decimal type. 
Combine Arrays
You can combine arrays together using a variety of methods of combining.
Source:
array1  array2 

["1","2","3"]  ["A","B","C"] 
["4","5","6"]  ["D","E","F"] 
["7","8","9"]  ["G","H","I"] 
The following transformation concatenates the above arrays into a single single array:
Transformation Name  New formula 

Parameter: Formula type  Single row formula 
Parameter: Formula  ARRAYCONCAT([array1,array2]) 
Parameter: New column name  arrayConcat 
Results:
array1  array2  arrayConcat 

["1","2","3"]  ["A","B","C"]  ["1","2","3","A","B","C"] 
["4","5","6"]  ["D","E","F"]  ["4","5","6","D","E","F"] 
["7","8","9"]  ["G","H","I"]  ["7","8","9","G","H","I"] 
These functions can be used to combine arrays together:
Function  Description 

ARRAYCONCAT Function  Combines the elements of one array with another, listing all elements of the first array before listing all elements of the second array. 
ARRAYCROSS Function  Generates a nested array containing the crossproduct of all elements in two or more arrays. 
ARRAYINTERSECT Function  Generates an array containing all elements that appear in multiple input arrays, referenced as column names or array literals. 
ARRAYSTOMAP Function  Combines one array containing keys and another array containing values into an Object of keyvalue pairs. 
ARRAYZIP Function  Combines multiple arrays into a single nested array, with element 1 of array 1 paired with element 2 of array 2 and so on. Arrays are expressed as column names or as array literals. 
Tip: Additional examples are available in the above links for these functions.
Break out Arrays
Expand arrays into rows
You can break out arrays into individual values using the following transformations. Here is some example data from the nest2
column that was generated earlier. The num3
column is retained for reference:
num3  nest2 

13  [[11,12],13] 
16  [[14,15],16] 
19  [[17,18],19] 
You can use the following simple transformation to flatten the values in nest2
into individual values in each row:
NOTE: Depending on the number of elements in your arrays, you can significantly increase the size of your dataset.
NOTE: If a cell in the source column does not contain an array, an empty value is written into the corresponding row.
Transformation Name  Convert Array to Rows 

Parameter: column  nest2 
Results:
num3  nest2 

13  [11,12] 
13  13 
16  [14,15] 
16  16 
19  [17,18] 
19  19 
NOTE: Converting a column of arrays to rows unpacks the top level of the array only. You may have to apply this transformation multiple times.
Unnest array elements into columns
You can break out individual elements of an array into separate columns.
NOTE: Each element that you want broken out into a column must be listed on a separate line in Path to elements.
Source:
arrayNested 

["A",["B","C"],"D"] 
["H",["I","J",["K","L"]]] 
["E","F","G"] 
The following transform retrieves the second and third elements of each array:
Transformation Name  Unnest Objects into columns 

Parameter: Column  arrayNested 
Parameter: Paths to elements1  [1] 
Parameter: Paths to elements2  [2] 
Parameter: Include original column name  true 
This one retrieves the first element of the array that is nested as the second element of the array:
Transformation Name  Unnest Objects into columns 

Parameter: Column  arrayNested 
Parameter: Paths to elements1  [1][0] 
Parameter: Include original column name  true 
The resulting data should look like the following:
arrayNested  arrayNested_1  arrayNested_2 

["A",["B","C"],"D"]  ["B","C"]  B 
["H",["I","J",["K","L"]]]  ["I","J",["K","L"]]  I 
["E","F","G"]  F 
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