Group by name and caluclate average $avg
- $avg
db.simple.aggregate( [ { $group: { _id: "$name", total: { $avg : "$cnt" } } } ] )
{
"result": [
{
"_id": "bar",
"total": 7
},
{
"_id": "foo",
"total": 4
}
],
"ok": 1
}