An aggregation method reduces the performance values of the test (and possibly the training sets) to a single value. To see all possible implemented aggregations look at aggregations.
The aggregation can access all relevant information of the result after resampling and combine them into a single value. Though usually something very simple like taking the mean of the test set performances is done.
Object members:
character(1))Name of the aggregation method.
character(1))Long name of the aggregation method.
Properties of the aggregation.
Aggregation function.