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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.

  • If an input value is missing or null, it is not factored in the computation. For example, for the first row in the dataset, the rolling count of distinct values of previous values is undefined.

  • The row from which to extract a value is determined by the order in which the rows are organized based on the order parameter.

  • If you are working on a randomly generated sample of your dataset, the values that you see for this function might not correspond to the values that are generated on the full dataset during job execution.

  • The function takes a column name and three optional integer parameters that determine the maximum number of values and the window backward and forward of the current row.

    • By default, the list is limited to 1000 values. To change the maximum number of values, specify a value for the limit parameter.

    • For the window parameters, the default values are -1 and 0, which computes the rolling function from the current row back to the first row of the dataset.

  • This function works with the Window transform. See Window Transform.

For more information on a non-rolling version of this function, see LIST Function.

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

Column example:

rollinglist(myCol)

Output: Returns the rolling list of values in the myCol column from the first row of the dataset to the current one.

Rows before example:

rollinglist(myNumber, 5, 20)

Output: Returns the rolling list of values of the current row and the twenty previous row values in the myNumber column, with a limit of 5 total values.

Rows before and after example:

rollinglist(myNumber, 20, 299, 200)

Output: Returns the rolling list of values from the previous 299 rows, the current row value, and the 200 rows after the current one in the myNumber column, with a limit of 20 total values.

Syntax and Arguments

rollinglist(col_ref, rowsBefore_integer, rowsAfter_integer) order: order_col [group: group_col]

Argument

Required?

Data Type

Description

col_ref

Y

string

Name of column whose values are applied to the function

limit_int

N

integer

Maximum number of values to extract into the list array. From 1 to 1000.

rowsBefore_integer

N

integer

Number of rows before the current one to include in the computation

rowsAfter_integer

N

integer

Number of rows after the current one to include in the computation

For more information on the order and group parameters, see Window Transform.

For more information on syntax standards, see Language Documentation Syntax Notes.

col_ref

Name of the column whose values are used to compute the function.

  • Multiple columns and wildcards are not supported.

Usage Notes:

Required?

Data Type

Example Value

Yes

String (column reference to Integer or Decimal values)

myColumn

limit_int

Non-negative integer that defines the maximum number of values to extract into the list array.

注意

If specified, this value must between 1 and 1000, inclusive.

注意

Do not use the limiting argument in a LIST function call on a flat aggregate, in which all values in a column have been inserted into a single cell. In this case, you might be able to use the limit argument if you also specify a group parameter. Misuse of the LIST function can cause the application to crash.

Usage Notes:

Required?

Data Type

Example Value

No

Integer

50

rowsBefore_integer, rowsAfter_integer

Integers representing the number of rows before or after the current one from which to compute the rolling function, including the current row. For example, if the first value is 5, the current row and the four rows after it are used in the computation. Negative values for rowsAfter_integer compute the rolling function from rows preceding the current one.

  • rowBefore=1 generates the current row value only.

  • rowBefore=-1 uses all rows preceding the current one.

  • If rowsAfter is not specified, then the value 0 is applied.

  • If a group parameter is applied, then these parameter values should be no more than the maximum number of rows in the groups.

Usage Notes:

Required?

Data Type

Example Value

No

Integer

4

Examples

提示

For additional examples, see Common Tasks.

Example - Recent Finishers by Boat Type

The following dataset includes the finishing times for each boat in a race. As part of the race, each boat may be assigned one or more penalties in terms of seconds. So, the total time for the race is computed by adding two columns.

You are interested in the list of recent finishers by each finishing time.

Source:

id

pilotName

boatType

raceTime

racePenalties

1

Schmidt

Sunfish

4573.8

53

2

Bolt

Laser

4934.21

11

3

Masters

Force 5

4446.89

70

4

Jamison

Force 5

4355.79

31

5

Williams

Sunfish

4675.86

15

6

Hobart

Laser

5077.5

50

7

Millingham

Laser

4940.09

54

8

Nelson

Force 5

5116.14

56

9

Greene

Sunfish

5105.94

5

10

Danielson

Laser

4964.03

18

11

Cooper

Force 5

5281.55

13

12

Stevens

Laser

5176.35

0

13

Young

Sunfish

5038.11

16

14

Thompson

Force 5

5252.9

62

15

McDonald

Laser

5052.24

20

16

O'Roarke

Sunfish

5080.76

45

17

Collins

Sunfish

5176.09

10

18

Wright

Laser

5391.61

34

19

Black

Sunfish

5023.32

32

20

Bush

Force 5

5200.37

28

Transformation:

Compute the total time for each racer by summing the raceTime column and the racePenalties column:

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: raceTime + racePenalties

FCTN(input)

Parameter: New column name

'totalRaceTime'

You can then compute the list of recent finishers by boat type, automatically sorting the generated lists by the totalRaceTime column:

Transformation Name

New formula

Parameter: Formula type

Multiple row formula

Parameter: Formula

rollinglist(boatType, 10, 4, 0)

Parameter: Order rows by

totalRaceTime

Parameter: New column name

'last5FinisherBoatTypes'

Results:

id

pilotName

boatType

last5FinisherBoatTypes

raceTime

racePenalties

totalRaceTime

4

Jamison

Force 5

["Force 5"]

4355.79

31

4386.79

3

Masters

Force 5

["Force 5","Force 5"]

4446.89

70

4516.89

1

Schmidt

Sunfish

["Force 5","Force 5","Sunfish"]

4573.8

53

4626.8

5

Williams

Sunfish

["Force 5","Force 5","Sunfish","Sunfish"]

4675.86

15

4690.86

2

Bolt

Laser

["Force 5","Force 5","Sunfish","Sunfish","Laser"]

4934.21

11

4945.21

10

Danielson

Laser

["Force 5","Sunfish","Sunfish","Laser","Laser"]

4964.03

18

4982.03

7

Millingham

Laser

["Sunfish","Sunfish","Laser","Laser","Laser"]

4940.09

54

4994.09

13

Young

Sunfish

["Sunfish","Laser","Laser","Laser","Sunfish"]

5038.11

16

5054.11

19

Black

Sunfish

["Laser","Laser","Laser","Sunfish","Sunfish"]

5023.32

32

5055.32

15

McDonald

Laser

["Laser","Laser","Sunfish","Sunfish","Laser"]

5052.24

20

5072.24

9

Greene

Sunfish

["Laser","Sunfish","Sunfish","Laser","Sunfish"]

5105.94

5

5110.94

16

O'Roarke

Sunfish

["Sunfish","Sunfish","Laser","Sunfish","Sunfish"]

5080.76

45

5125.76

6

Hobart

Laser

["Sunfish","Laser","Sunfish","Sunfish","Laser"]

5077.5

50

5127.5

8

Nelson

Force 5

["Laser","Sunfish","Sunfish","Laser","Force 5"]

5116.14

56

5172.14

12

Stevens

Laser

["Sunfish","Sunfish","Laser","Force 5","Laser"]

5176.35

0

5176.35

17

Collins

Sunfish

["Sunfish","Laser","Force 5","Laser","Sunfish"]

5176.09

10

5186.09

20

Bush

Force 5

["Laser","Force 5","Laser","Sunfish","Force 5"]

5200.37

28

5228.37

11

Cooper

Force 5

["Force 5","Laser","Sunfish","Force 5","Force 5"]

5281.55

13

5294.55

14

Thompson

Force 5

["Laser","Sunfish","Force 5","Force 5","Force 5"]

5252.9

62

5314.9

18

Wright

Laser

["Sunfish","Force 5","Force 5","Force 5","Laser"]

5391.61

34

5425.61

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