Mongodb: $round decimal

Question

I'm trying to round the average salary to 2 decimal places. I'm stumped, I can get either everyones salary to 2 decimal places

db.employees.aggregate([{$project: {_id: null, 'roundedSal':{$round: [{$avg: '$salary'}]}}}])

which returns

{ "_id": null, "roundedSal": 48501.24 } { "_id": null, "roundedSal": 45999.71 } { "_id": null, "roundedSal": 35554.54 } { "_id": null, "roundedSal": 47700 } { "_id": null, "roundedSal": 48123.25 } { "_id": null, "roundedSal": 44415.94 } { "_id": null, "roundedSal": 42925.26 } { "_id": null, "roundedSal": 31500.66 } { "_id": null, "roundedSal": 50500.25 }

or get the overall average

db.employees.aggregate([{$group: {_id: null, 'roundedSal':{$avg: '$salary'}}}])

{ "_id" : null, "roundedSal" : 43913.427777777775 }

but I can't manage to figure out how to round this to two decimal places without an error being thrown

Answer 1

Please read the mongo documentation it's one of the bestest documentantions in my opinion.

// { $round : [ <number>, <place> ] }

db.employees.aggregate([{$project: {_id: null, 'roundedSal':{$round: [{$avg: '$salary'}, 2]}}}])