Differ() isn't a robust way of differentiating facilities because of the way EPA stores program IDs.

[ericnost]

This isn't a robust way of differentiating facilities because of the way EPA stores program IDs.

The differ function is meant to take data like:
all_facilities = [A, B, C, D, E]
facilities_with_inspections = [C, D]
and calculate:
facilities_without_inspections = [A, B, E]

But in reality, facility/program IDs are more like:
all_facilities = [A X, B Y, C, D Z, E]
facilities_with_inspections = [C, D]
So the resulting list of facilities without inspections would incorrectly be:
A X, B Y, D Z
even though D does have an inspection.

Just need a way to parse apart program IDs, ideally without having to call up the database to look at the EXP_PGM table.

Originally posted by @ericnost in #50 (comment)