$ln
The $ln operator calculates the natural logarithm of the input
$ln
The $ln operator calculates the natural logarithm (base e) of the input number.
Examples
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
}
]
}
]
}Example 1 - Calculate the natural logarithm of total sales by category
To calculate the natural logarithm of sales volume by category to analyze growth rates, run a query using the $ln operator on the totalSales field to return the desired result.
db.stores.aggregate([{
$match: {
_id: "40d6f4d7-50cd-4929-9a07-0a7a133c2e74"
}
},
{
$project: {
name: 1,
salesGrowthMetrics: {
$map: {
input: "$sales.salesByCategory",
as: "category",
in: {
categoryName: "$$category.categoryName",
salesValue: "$$category.totalSales",
naturalLog: {
$ln: "$$category.totalSales"
}
}
}
}
}
}
])This query returns the following result:
[
{
"_id": "40d6f4d7-50cd-4929-9a07-0a7a133c2e74",
"name": "Proseware, Inc. | Home Entertainment Hub - East Linwoodbury",
"salesGrowthMetrics": [
{
"categoryName": "Sound Bars",
"salesValue": 2120,
"naturalLog": 7.659
},
{
"categoryName": "Home Theater Projectors",
"salesValue": 45004,
"naturalLog": 10.714
},
{
"categoryName": "Game Controllers",
"salesValue": 43522,
"naturalLog": 10.681
},
{
"categoryName": "Remote Controls",
"salesValue": 28946,
"naturalLog": 10.273
},
{
"categoryName": "VR Games",
"salesValue": 32272,
"naturalLog": 10.382
}
]
}
]