Database
[{averages:[["Object"],["Object"],["Object"],["Object"],["Object"],["Object"],["Object"]]},{averages:[["Object"],["Object"],["Object"],["Object"],["Object"],["Object"],["Object"]]},{averages:[["Object"],["Object"],["Object"],["Object"],["Object"],["Object"],["Object"]]},{averages:"No data in period."}]
Query
db.collection.aggregate([{"$match":{"averages":{"$type":"array"}}}])