适用对象：
MongoDB vCore
该 $log10 运算符计算数字的对数 10 基数并返回结果。
语法
运算符的 $isArray 语法如下所示：
{ $log10: <number> }
参数
| DESCRIPTION | |
|---|---|
<number> |
解析为正数的任何有效表达式。 |
示例：
让我们了解数据集中的示例数据的 stores 使用情况，以使用对数刻度分析销售分布。
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"
}
}
}
}
}
}
}
])
这将生成以下输出：
{
"_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"
}
]
}