|  | ## Aggregate

#### Synopsis

Performs one of the aggregation functions (count, sum...) known from SQL (allows also grouping).

#### Description

This operator creates a new example set from the input example set showing the results of arbitrary aggregation functions (as SUM, COUNT etc. known from SQL). Before the values of different rows are aggregated into a new row the rows might be grouped by the values of a multiple attributes (similar to the group-by clause known from SQL). In this case a new line will be created for each group.

Please note that the known HAVING clause from SQL can be simulated by an additional ExampleFilter operator following this one.

#### Input

- example set input: expects: ExampleSetMetaData: #examples: = 0; #attributes: 0

#### Output

- example set output:
- original:

#### Parameters

- aggregation attributes: The attributes which should be aggregated.
- group by attributes: Performs a grouping by the values of the attributes whose names match the given regular expression.
- count all combinations: Indicates that all possible combinations of the values of the group by attributes are counted, even if they don't occur. Please handle with care, since the number might be enormous.
- only distinct: Indicates if only rows with distinct values for the aggregation attribute should be used for the calculation of the aggregation function.
- ignore missings: Indicates if missings should be ignored and aggregation should be based only on existing values or not. In the latter case the aggregated value will be missing in the presence of missing values.

#### ExampleProcess