aggr?

[#1]

aggr(Avg(Total <Batch> Value), Batch)

how it caluclate?

[#2]

the aggr function makes a list.

So in your example you might have Batches: A, B, C, D, E....

Each of your Batches will have numerous values associated with them..

So your aggr function creates a list of average values based on Batch. For example:

avg(values associated with A)

avg(values associated with B)

avg(values associated with C)

avg(values associated with D)

avg(values associated with E)