Given a large volume of data, we want to determine the average of a certain field, grouped by some other field.
This is a very simple exercise, and it probably does not constitute a pattern, but it does provide a useful introduction to PhixFlow and the aggregate functions built into the pipe functionality.
Solution:
Create a stream (loaded from a file is fine) containing a list of countries, years and populations
Create second stream from the data in the first stream
Configure the pipe that joins the 2 streams to calculate the average population, grouped by country
