Back to DocumentationMQL Documentation

$expMovingAvg

Calculates the exponential moving average of field values, giving higher weight to recent documents in the calculation for trend analysis.

Syntax

{ $expMovingAvg: { input: <field>, N: <number> } }

Parameters

inputobjectrequired

Field whose values are used to calculate the exponential moving average

Nnumber

Number of previous documents with highest weight in calculation

alphanumber

Decay rate parameter, higher values give less weight to previous documents

Examples

Calculate exponential moving average of total sales

Compute exponential moving average with highest weight on 2 recent documents

Query:

db.stores.aggregate([{ $match: { "company": { $in: ["First Up Consultants"] } } }, { $setWindowFields: { "partitionBy": "$company", "sortBy": { "storeOpeningDate": 1 }, "output": { "expMovingAvgForSales": { "$expMovingAvg": { "input": "$sales.totalSales", "N": 2 } } } } }])

Output:

Stores with exponential moving average of sales using 2-document weight

Calculate exponential moving average using alpha parameter

Use decay rate parameter for exponential moving average calculation

Query:

db.stores.aggregate([{ $match: { "company": { $in: ["First Up Consultants"] } } }, { $setWindowFields: { "partitionBy": "$company", "sortBy": { "storeOpeningDate": 1 }, "output": { "expMovingAvgForSales": { "$expMovingAvg": { "input": "$sales.totalSales", "alpha": 0.75 } } } } }])

Output:

Stores with exponential moving average using 0.75 alpha decay rate

Related