ROLLINGCOUNTA Function

Computes the rolling count of non-null values forward or backward of the current row within the specified column.

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 non-null 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 two optional integer parameters that determine the window backward and forward of the current row.
- The default integer parameter 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 COUNTA 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:

rollingcounta(myCol)

Output: Returns rolling count of non-null values in the myCol column.

Rows before example:

rollingocounta(myNumber, 3)

Output: Returns the rolling count of non-null values of the current row and the three previous row values in the myNumber column.

Rows before and after example:

rollingcounta(myNumber, 3, 2)

Output: Returns the rolling count of non-nulls from the three previous row values, the current row value, and the two rows after the current one in the myNumber column.

Syntax and Arguments

rollingcounta(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
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

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 five rows before it are used in the computation. Negative values for rowsAfter_integer compute the rolling function from rows preceding the current one.

rowBefore=0 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 - Counting messages

In the following example, messages are tabulated every 10 seconds from a system. If no message is generated, null values are returned.

Source:

Timestamp	msgType	msgDescription
15:10:00 PM	warning	Server restarted.
15:10:10 PM	warning	Unable to locate patterns file.
15:10:20 PM
15:10:30 PM
15:10:40 PM	error	Cannot connect to data source.
15:10:50 PM	error	Cannot open dataset.
15:11:00 PM
15:11:10 PM
15:11:20 PM	error	Insufficient permissions to write to target location.
15:11:30 PM
15:11:40 PM	warning	Server restarted.
15:11:50 PM	warning	Unable to locate patterns file.
15:12:00 PM	error	Data node offline.
15:12:10 PM
15:12:20 PM
15:12:30 PM	warning	Invalid statement in recipe.
15:12:40 PM
15:12:50 PM

Transformation:

You are interested in counting the number of entries for the preceding minute for each row. You add the following:

Transformation Name	`New formula`
Parameter: Formula type	Multiple row formula
Parameter: Sort rows by	Timestamp
Parameter: Formula	rollingcounta(msgType, 5, 0)
Parameter: New column name	'rollingcounta_msgType'

Results:

Timestamp	msgType	msgDescription	rollingcounta_msgType
15:10:00 PM	warning	Server restarted.	1
15:10:10 PM	warning	Unable to locate patterns file.	2
15:10:20 PM			2
15:10:30 PM			2
15:10:40 PM	error	Cannot connect to data source.	3
15:10:50 PM	error	Cannot open dataset.	4
15:11:00 PM			3
15:11:10 PM			2
15:11:20 PM	error	Insufficient permissions to write to target location.	3
15:11:30 PM			3
15:11:40 PM	warning	Server restarted.	3
15:11:50 PM	warning	Unable to locate patterns file.	3
15:12:00 PM	error	Data node offline.	4
15:12:10 PM			4
15:12:20 PM			3
15:12:30 PM	warning	Invalid statement in recipe.	4
15:12:40 PM			3
15:12:50 PM			2

本节内容如下: