With Category Aggregator, you can store a collection of collections. The entire collection is identified by a unique name. You can apply several aggregating functions to each of the contained collections. It is not possible to select a single value from a specific collection.
The category aggregator provides the following functions (each function takes into account only those values belonging to the currently active value of the given data field):
Sum([Field])
This function returns the sum of all values currently contained in the collection.
Avg([Field])
This function returns the average of all values currently contained in the collection.
Stdev([Field])
This function returns the standard deviation of all values currently contained in the collection.
Prsd([Field])
This function returns the relative standard deviation (Stdev/Avg*100) of all values currently contained in the collection.
Min([Field])
This function returns the lowest value currently contained in the collection.
Max([Field])
This function returns the highest value currently contained in the collection.
Count([Field])
This function returns the number of elements in the collection.
Clear([Field])
This function deletes all values from the collection. At the same time, it returns the number of deleted values.
A sample has been injected several times. One specific compound has been detected in each injection. For each sample, a collection of the retention times is created. These collections are addressed via the sample name. All of those collections are contained in a category aggregator named CatRetentionTimes.
You can return the average retention time for each sample with Avg(CatRetentionTimes(Sample_Name)). The argument in the brackets defines the specific category, that is, the portion of values contained in CatRetentionTimes to which the Avg function is applied.
You may use this expression, for example, in a composite group that is repeated on the sample name. The average retention times are then automatically calculated and shown for each sample name.