Aggregation is the process, where values from the records in the database, that correspond to a particular node, are totalled, averaged or processed. They are then stored along with other details of that node.

A typical aggregation might calculate the total of a particular field in the records associated with each node.

Each aggregation are defined by an aggregation type and one of more parameters, which include fields, constants, previous aggregations and file names.

Daisy has around 70 different aggregation types, which fall loosely into four groups :-

• Ones, such as Total, Average and Standard Devation, that act directly on one or more fields in the database to produce the aggregation.

• Others perform arithmetic operations, such as Add, Multiply and Divide on previous aggregations.

• Counts can be performed on fields, which can be expressed directly or as a percentage.

• Values can be extracted from tables depending on the values of an aggregation.

See Aggregation in the Help for more details.