CODEWITHSUNDEEP
mongodbmongoose
e.k
e.k

Reputation: 1363

How to calculate average in mongoose?

My schema looks like 

point: { type: Number, default: 0 },
effort: { type: Number, default: 0 },
note: { type: String },
dateRated: {type: Date},
createDate: {type:Date},
dateInfoId: {type: String}

I'm trying to calculate average of point and effort by passing certain _id's

My code looks like 

frequencies = ["mongo object id"];
Frequency.aggregate([{
    $project: {
        _id: {
            $in: ['$_id', frequencies]
        },
        point: {
            $ne: ['$point', 0]
        }
    }
}, {
    $group: {
        _id: {
            $in: ['$_id', frequencies]
        },
        average: {
            $avg: "$point"
        },
        effort: {
            $avg: "$effort"
        }
    }
}], (err, result) => {});

But it always returns [ { _id: false, average: null, effort: null } ]. What should I do to calculate the average of my points and effort?

Upvotes: 2

Views: 858

Answers (1)

whoami - fakeFaceTrueSoul
whoami - fakeFaceTrueSoul

Reputation: 17915

It has to be like this :

Frequency.aggregate([{
    $match: {
        _id: {
            $in: frequencies
        }, point: { $ne: 0 }
    }
}, {
    $group: {
        _id: null,
        average: {
            $avg: "$point"
        },
        effort: {
            $avg: "$effort"
        }
    }
}])

Here $match would retain only the documents that match with passed frequencies and where point != 0, then after all you need is to iterate through all documents to get the average of required two fields, So $group helps to do that, where _id: null or _id: '' will iterate through all of the leftover documents, you no need to specify a filter again in group stage.

Upvotes: 1

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