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
and0
, 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 value0
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
Astuce
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 | |
---|---|
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 |