Aggregate Functions

These are aggregate functions as available on stream views and pipes. Aggregate functions serve the purpose of aggregating data and giving it more meaningful meaning. They are usually a common feature in any data based environment. In database management, for instance aggregate functions are used where multiple rows are grouped together to form a singe value or to find out more significant meaning, represented by a single value on a set of values.

Aggregate functions are also available on pipes and views in PhixFlow. The following comprises a set of available functions (all aggregate function below expect a single argument - field name):

Function

Description

Average

This function returns the arithmetic average value of an attribute with the same grouping field values.

In detail, it returns the sum of all values with the same grouping field values divided by the number of values that are not null.

It is only available for numeric attributes.

Maximum

This function returns the maximum value of an attribute with the same grouping field values.

It is available for numeric, string and date/time attributes.

Strings are ordered alphabetically, with the shortest strings first.

Minimum

This function returns the minimum value of an attribute with the same grouping field values.

It is available for numeric, string and date/time attributes.

Strings are ordered alphabetically, with the shortest strings first.

Sum

This function returns the sum of all the values of an attribute with the same grouping field values.

It is only available for numeric attributes.

Percent

This function expects a name of numeric field to calculate percentage of sum of numerical values of each group in relation to a whole set of grouped values.

It is therefore necessary to use this function in conjunction with grouping attribute, as otherwise only default grouping would be applied and this would present no meaningful result, as it would always default to 100% (each record would have been in its own group). If however we assume having a file with 2 records, like so:

Number	Label
12	A
14	B
13	C
10	A
5	A
2	B

and we also assume grouping by "Label", our percent function would return (if applied o "Number" attribute), the following result in a view (assuming we also selected Label attribute to be shown in our view and rounding to 2 decimal places):

Number	Label
48.22	A
28.57	B
23.21	C

The above are percentages of values assigned to given grouping parameters (A, B, C) as a percentage portion of the whole, computed as sum of all such values.

Distinct

This function returns the number of unique values for the given attribute with the same grouping field values.

Count

This function returns the number of non-null values with the same grouping field values.