Question 115489 in Mongodb Question posted in
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Mongodb – How to calculate average records per month?

My records like this [{ createdAt }, {createdAt}, {createdAt} ]

I need average records per month.

january => 3 records
february => 2 records etc..
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2

Answers


  1. 0

    You can try to $group by month and year when counting and by month when averaging:

    db.collection.aggregate([
  {
    $group: {
      _id: {
        month: {
          $month: "$createdAt"
        },
        year: {
          $year: "$createdAt"
        },
        
      },
      count: {
        $sum: 1
      }
    }
  },
  {
    $group: {
      _id: {
        month: "$_id.month"
      },
      average: {
        $avg: "$count"
      }
    }
  },
  {
    $project: {
      _id: 0,
      month: "$_id.month",
      average: 1
    }
  }
])

    Link to playground

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  2. 0

    Not fully clear what you mean by "average records per month" but I think it would be this:

    db.collection.aggregate([
   {
      $group: {
         _id: {
            $dateTrunc: {
               date: "$createdAt",
               unit: "month"
            }
         },
         count: { $count: {} }
      }
   },
   {
      $group: {
         _id: null,
         data: { $push: { k: { $toString: { $month: "$_id" } }, v: "$count" } }
      }
   },
   { $replaceWith: { $arrayToObject: "$data" } }
])

    Getting the month name is not so easy, either you use a external library or build your own with $switch

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