$abs

The `$abs` operator returns the absolute value of a number. It removes any negative sign from a number, making it positive.

Syntax

{ $abs: <expression> }

Parameters

<expression>stringrequired

Any expression that resolves to a number. If the expression is null or refers to a missing field, $abs returns null.

Examples

Sample Data

{
  "_id": "0fcc0bf0-ed18-4ab8-b558-9848e18058f4",
  "name": "First Up Consultants | Beverage Shop",
  "sales": {
    "salesByCategory": [
      { "categoryName": "Wine Accessories", "totalSales": 34440 }
    ]
  }
}

Use the absolute value of total sales

Calculate the absolute difference in sales volume of each category and the average sales across all categories for a store.

Query:

db.stores.aggregate([
  { $match: { _id: "40d6f4d7-50cd-4929-9a07-0a7a133c2e74" } },
  {
    $project: {
      name: 1,
      salesByCategory: {
        $map: {
          input: "$sales.salesByCategory",
          as: "category",
          in: {
            categoryName: "$$category.categoryName",
            totalSales: "$$category.totalSales",
            differenceFromAverage: {
              $abs: {
                $subtract: [
                  "$$category.totalSales",
                  { $avg: "$sales.salesByCategory.totalSales" }
                ]
              }
            }
          }
        }
      }
    }
  }
])

Output:

[
  {
    "_id": "40d6f4d7-50cd-4929-9a07-0a7a133c2e74",
    "name": "Proseware, Inc. | Home Entertainment Hub",
    "salesByCategory": [
      { "categoryName": "Sound Bars", "totalSales": 2120, "differenceFromAverage": 28252.8 }
    ]
  }
]