ARRAYELEMENTAT Function
Computes the 0-based index value for an array element in the specified column, array literal, or function that returns an array.
This function calculates based on the outer layer of an array. If your array is nested, the count of inner elements is not factored.
If a row contains a missing array, the returned value is
0. If it contains a value that is not recognized as an array, the returned value is null.
Wrangle vs. SQL: This function is part of Wrangle, a proprietary data transformation language. Wrangle is not SQL. For more information, see Wrangle Language.
Basic Usage
Array literal reference example:
arrayelementat([A,B,C,D],2)
Output: Returns the third value in the array, which is C.
Column reference example:
arrayelementat(myArrays,9)
Output: Returns the tenth element of the arrays listed in the myArrays column.
Array function example:
arrayelementat(concat([colA,colB]),3)
Output: Returns the fourth element of the concatenated array.
Syntax and Arguments
arrayelementat(array_ref,int_index_ref)
Argument | Required? | Data Type | Description |
|---|---|---|---|
array_ref | Y | string | Name of Array column, Array literal, or function returning an Array to apply to the function |
int_index_ref | Y | integer (non-negative) | Index value for the array element to return. Value can be Integer literal, column containing Integer values, or function returning an Integer. |
For more information on syntax standards, see Language Documentation Syntax Notes.
array_ref
Name of the array column, array literal, or function returning an array whose elements you want to return.
Multiple columns and wildcards are not supported.
Usage Notes:
Required? | Data Type | Example Value |
|---|---|---|
Yes | String (column reference or function) or array literal | myArray1 |
int_index_ref
Non-negative integer value representing the index value of the array element to return. Value can be Integer literal, column containing Integer values, or function returning an Integer.
Value must a non-negative integer. If the value is
0, then the first element of the array is returned.If this value is greater than the length of the string, then a null value is returned.
Usage Notes:
Required? | Data Type | Example Value |
|---|---|---|
Yes | Integer (non-negative) | 5 |
Examples
Astuce
For additional examples, see Common Tasks.
Example - Student progress across tests
This example illustrates how to return n-based number of elements in an array.
Functions:
Item | Description |
|---|---|
ARRAYLEN Function | Computes the number of elements in the arrays in the specified column, array literal, or function that returns an array. |
ARRAYELEMENTAT Function | Computes the 0-based index value for an array element in the specified column, array literal, or function that returns an array. |
ARRAYSORT Function | Sorts array values in the specified column, array literal, or function that returns an array in ascending or descending order. |
Source:
Here are some student test scores. Individual scores are stored in the Scores column. You want to:
Flag the students who have not taken four tests.
Compute the range in scores for each student.
LastName | FirstName | Scores |
|---|---|---|
Allen | Amanda | [79, 83,87,81] |
Bell | Bobby | [85, 92, 94, 98] |
Charles | Cameron | [88,81,85] |
Dudley | Danny | [82,88,81,77] |
Ellis | Evan | [91,93,87,93] |
Transformation:
First, you want to flag the students who did not take all four tests:
Transformation Name | |
|---|---|
Parameter: Formula type | Single row formula |
Parameter: Formula | IF(ARRAYLEN(Scores) < 4,"incomplete","") |
Parameter: New column name | 'Error' |
This test flags Cameron Charles only.
The following transform sorts the array values in highest to lowest score:
Transformation Name | |
|---|---|
Parameter: Columns | Scores |
Parameter: Formula | ARRAYSORT(Scores, 'descending') |
The following transforms extracts the first (highest) and last (lowest) value in each student's test scores, provided that they took four tests:
Transformation Name | |
|---|---|
Parameter: Formula type | Single row formula |
Parameter: Formula | ARRAYELEMENTAT(Scores,0) |
Parameter: New column name | 'highestScore' |
Transformation Name | |
|---|---|
Parameter: Formula type | Single row formula |
Parameter: Formula | ARRAYELEMENTAT(Scores,3) |
Parameter: New column name | 'lowestScore' |
Astuce
You could also generate the Error column when the Scores4 column contains a null value. If no value exists in the array for the ARRAYELEMENTAT function, a null value is returned, which would indicate in this case an insufficient number of elements (test scores).
You can now track change in test scores:
Transformation Name | |
|---|---|
Parameter: Formula type | Single row formula |
Parameter: Formula | SUBTRACT(highestScore,lowestScore) |
Parameter: New column name | 'Score_range' |
Results:
LastName | FirstName | Scores | Error | lowestScore | highestScore | Score_range |
|---|---|---|---|---|---|---|
Allen | Amanda | [87,83,81,79] | 79 | 87 | 8 | |
Bell | Bobby | [98,94,92,85] | 85 | 98 | 13 | |
Charles | Cameron | [88,85,81] | incomplete | 88 | ||
Dudley | Danny | [88,82,81,77] | 77 | 88 | 11 | |
Ellis | Evan | [93,93,91,87] | 87 | 93 | 6 |