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Function Name Description Parameters Examples

Count

Outputs the number of steam elements.

Name	Description	Default Value	Optional?
`OUTPUT_ATTRIBUTES`	The name for the output attribute.	`count`	True

['FUNCTION' = 'Count']

['FUNCTION' = 'Count', 'OUTPUT_ATTRIBUTES' = 'number_of_elements']

Sum

Outputs the sum of elements.

Name	Description	Default Value	Optional?
INPUT_ATTRIBUTES	The single string or a list of the name(s) of the attribute(s) in the input tuples. By default, all input attributes are used. This could raise an error if attributes are not numeric.	(all attributes)	True
OUTPUT_ATTRIBUTES	A single string or list of output attributes. By default, the string "Sum_" concatenated with the original input attribute name is used.	"Sum_" + intput attribute name	True

['FUNCTION' = 'Sum']

['FUNCTION' = 'Sum', 'INPUT_ATTRIBUTES' = 'value1']

['FUNCTION' = 'Sum', 'INPUT_ATTRIBUTES' = ['value1', 'value2']]

Avg Average value (mean) TODO (similar to Sum)

Min Min value TODO (similar to Sum)

Max Max value TODO (similar to Sum)

First

The first element of a window. See example below.

Name	Description	Default Value	Optional?
`OUTPUT_ATTRIBUTES`	The name for the output attribute.	`first`	True

You should use the following settings:

output_only_changes = true

This results in getting the first element in each window. Especially useful with a tumbling window.

Last

The last element of a window. See example below.

Name	Description	Default Value	Optional?
`OUTPUT_ATTRIBUTES`	The name for the output attribute.	`last`	True

You should use the following settings:

EVAL_AT_NEW_ELEMENT = false
EVAL_BEFORE_REMOVE_OUTDATING = true

This results in getting the last element in each window. Especially useful with a tumbling window.

Trigger The tuple that triggers the output. TODO

Variance Calculates the variance TODO (similar to Sum)

TopK Calculates the top-K list TODO

Nest Nests the valid elements as list. TODO

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Code Block

language	js
linenumbers	true

/// count the number of items for each publisher
counted = AGGREGATION({AGGREGATIONS = [['FUNCTION' = 'Count']], GROUP_BY = ['publisher', 'item']}, windowed)
/// aggregate the 100 most frequent items for each publisher to an ordered list
TopKItemsByPublisher ::= AGGREGATION({AGGREGATIONS = [
	[
		'FUNCTION' = 'TopK',
		'TOP_K' = '100',                         /// number of items
		'SCORING_ATTRIBUTES' = 'Count',          /// the attribute name that defines the order
		'INPUT_ATTRIBUTES' = 'item',             /// do not use the whole input tuple, just use the 'item' attribute for creating the output top-k set
		'MIN_SCORE' = '0',                       /// remove items that reaches a score of 0 (due to the previous aggregation these are all items that has no valid tuple)
		'UNIQUE_ATTR'='item'                     /// use 'item' as a unique attribute. that means, a new tuple with an known items id replaces the previous value. (this is some kind of element window in this operator)
	]], GROUP_BY = ['publisher']}, counted)

First

TExt

Last

Here, we use a tumbling window and the "Last" aggregate function to only get the last element per 5-minute window.

Code Block

collapse	true

/// Tumnbling window
tumbling = TIMEWINDOW({
                size = [5, 'MINUTES'],
                advance = [5, 'MINUTES']                                                                                                
              },
              selectCenter
            )
            
/// Select first of tumbling
reduce = AGGREGATION({
              aggregations = [['FUNCTION' = 'Last']],
              EVAL_AT_NEW_ELEMENT = false,
              EVAL_BEFORE_REMOVE_OUTDATING = true,
              group_by = ['movingObjectId']               
            },
            tumbling
          )            
          
/// Remove the grouping id (because it will be in the unnested tuple)
withoutId = PROJECT({
                attributes = ['last']              
              },
              reduce
            )

/// Unnest the tuple
output = UNNEST({
              attribute='last'                                        
            },
            withoutId
          )

Changing the way this operator outputs values

By using the default values, this operator act as Aggregate (and Group) operator (with the limitations explained above). Useful alternative settings are:

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Old Version 7

New Version 8

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Changing the way this operator outputs values