$log10

The $log10 operator calculates the logarithm of a number in base 10 and returns the result.

{
  $log10: <number>
}

Consider this sample document from the stores collection.

{
    "_id": "0fcc0bf0-ed18-4ab8-b558-9848e18058f4",
    "name": "First Up Consultants | Beverage Shop - Satterfieldmouth",
    "location": {
        "lat": -89.2384,
        "lon": -46.4012
    },
    "staff": {
        "totalStaff": {
            "fullTime": 8,
            "partTime": 20
        }
    },
    "sales": {
        "totalSales": 75670,
        "salesByCategory": [
            {
                "categoryName": "Wine Accessories",
                "totalSales": 34440
            },
            {
                "categoryName": "Bitters",
                "totalSales": 39496
            },
            {
                "categoryName": "Rum",
                "totalSales": 1734
            }
        ]
    },
    "promotionEvents": [
        {
            "eventName": "Unbeatable Bargain Bash",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 6,
                    "Day": 23
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 7,
                    "Day": 2
                }
            },
            "discounts": [
                {
                    "categoryName": "Whiskey",
                    "discountPercentage": 7
                },
                {
                    "categoryName": "Bitters",
                    "discountPercentage": 15
                },
                {
                    "categoryName": "Brandy",
                    "discountPercentage": 8
                },
                {
                    "categoryName": "Sports Drinks",
                    "discountPercentage": 22
                },
                {
                    "categoryName": "Vodka",
                    "discountPercentage": 19
                }
            ]
        },
        {
            "eventName": "Steal of a Deal Days",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 9,
                    "Day": 21
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 9,
                    "Day": 29
                }
            },
            "discounts": [
                {
                    "categoryName": "Organic Wine",
                    "discountPercentage": 19
                },
                {
                    "categoryName": "White Wine",
                    "discountPercentage": 20
                },
                {
                    "categoryName": "Sparkling Wine",
                    "discountPercentage": 19
                },
                {
                    "categoryName": "Whiskey",
                    "discountPercentage": 17
                },
                {
                    "categoryName": "Vodka",
                    "discountPercentage": 23
                }
            ]
        }
    ]
}

To bucket the distribution of sales per category within a store, run a query using the $log10 operator on the totalSales field. Then, bucket the categories into "Low", "Medium" and "High" based on the result.

db.stores.aggregate([
  { $match: { "_id": "40d6f4d7-50cd-4929-9a07-0a7a133c2e74" } },
  {
    $project: {
      name: 1,
      salesAnalysis: {
        $map: {
          input: "$sales.salesByCategory",
          as: "category",
          in: {
            categoryName: "$$category.categoryName",
            originalSales: "$$category.totalSales",
            logScale: { $log10: "$$category.totalSales" },
            magnitudeClass: {
              $switch: {
                branches: [
                  { case: { $lt: [{ $log10: "$$category.totalSales" }, 3] }, then: "Low" },
                  { case: { $lt: [{ $log10: "$$category.totalSales" }, 4] }, then: "Medium" },
                  { case: { $lt: [{ $log10: "$$category.totalSales" }, 5] }, then: "High" }
                ],
                default: "Very High"
              }
            }
          }
        }
      }
    }
  }
])

This query returns the following result:

[
  {
    "_id": "40d6f4d7-50cd-4929-9a07-0a7a133c2e74",
    "name": "Proseware, Inc. | Home Entertainment Hub - East Linwoodbury",
    "salesAnalysis": [
      {
        "categoryName": "Sound Bars",
        "originalSales": 2120,
        "logScale": 3.326,
        "magnitudeClass": "Medium"
      },
      {
        "categoryName": "Home Theater Projectors",
        "originalSales": 45004,
        "logScale": 4.653,
        "magnitudeClass": "High"
      },
      {
        "categoryName": "Game Controllers",
        "originalSales": 43522,
        "logScale": 4.639,
        "magnitudeClass": "High"
      },
      {
        "categoryName": "Remote Controls",
        "originalSales": 28946,
        "logScale": 4.462,
        "magnitudeClass": "High"
      },
      {
        "categoryName": "VR Games",
        "originalSales": 32272,
        "logScale": 4.509,
        "magnitudeClass": "High"
      }
    ]
  }
]

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