Mongo average aggregation query with no group

Question

I am trying to get the average of a whole field using the aggregation framework in Mongo. However i can\'t seem to find any example that uses it without a group parameter. <

Answer 1

First of all store numerical values as numbers. Afterwards you can use a simple statement to calculate the average:

db.collection.aggregate({ 
  "$group": {
    "_id": null, 
    "avg_bvc": { "$avg": "$bvc" } 
  } 
})

You can simply use more $avg aggregation operators to get averages for your other numeric fields:

db.collection.aggregate({ 
  "$group": {
    "_id": null, 
    "avg_bvc": { "$avg": "$bvc" }, 
    "avg_dollar": { "$avg": "$dollar" } 
  } 
})