Aggregator

From Fmepedia

Aggregator is a Workbench Transformer.

Creates an aggregate of the input features. The Group By option can be used to limit this to sets of features that have one or more attributes in common.

There are several options for summing or averaging attributes, which can come in quite useful in certain cases. These options are also available through the various List transformers, but in order to use those you will have to set a List Name attribute.

Setting the Count attribute name will create an attribute which holds the number of original features that went into a certain aggregate.