$degreesToRadians (aggregation)

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Definition定义

$degreesToRadians

New in version 4.2.版本4.2中的新功能。

Converts an input value measured in degrees to radians.将以度为单位的输入值转换为弧度。

$degreesToRadians has the following syntax:语法如下所示：

{ $degreesToRadians: <expression> }

$degreesToRadians takes any valid expression that resolves to a number.接受任何解析为数字的有效表达式。

By default $degreesToRadians returns values as a double. 默认情况下，$degreesToRadians返回double值。$degreesToRadians can also return values as a 128-bit decimal as long as the <expression> resolves to a 128-bit decimal value.只要<expression>解析为128位十进制值，$degreesToRadians也可以以128位十进制返回值。

For more information on expressions, see Expressions.有关表达式的详细信息，请参阅表达式。

Behavior行为

null, NaN, and +/- Infinity

If the argument resolves to a value of null or refers to a field that is missing, $degreesToRadians returns null. 如果参数解析为null值或引用缺少的字段，$degreesToRadians返回null。If the argument resolves to NaN, $degreesToRadians returns NaN. 如果参数解析为NaN，$degreesToRadians返回NaN。If the argument resolves to negative or positive infinity, $degreesToRadians negative or positive infinity respectively.如果参数解析为负无穷大或正无穷大，则$degreesToRadians分别为负无穷大或正无穷大。

Example示例Results结果
{ $degreesToRadians: NaN } NaN
{ $degreesToRadians: null } null
{ $degreesToRadians : Infinity} Infinity
{ $degreesToRadians : -Infinity } -Infinity

Example示例

The trigonometry collection contains a document that contains three angles measured in degrees:trigonometry集合包含一个文档，其中包含以度为单位测量的三个角度：

{
  "angle_a" : NumberDecimal("53.13010235415597870314438744090659"),
  "angle_b" : NumberDecimal("36.86989764584402129685561255909341"),
  "angle_c" : NumberDecimal("90")
}

The following aggregation operation uses the $degreesToRadians expression to convert each value to its radian equivalent and add them to the input document using the $addFields pipeline stage.下面的聚合操作使用$degreesToRadians表达式将每个值转换为其等效的弧度，并使用$addFields管道阶段将它们添加到输入文档中。

db.trigonometry.aggregate([
  {
    $addFields: {
      "angle_a_rad" : { $degreesToRadians : "$angle_a"},
      "angle_b_rad" : { $degreesToRadians : "$angle_b"},
      "angle_c_rad" : { $degreesToRadians : "$angle_c"}
    }
  }
])

The operation returns the following document:该操作将返回以下文档：

{
  "_id" : ObjectId("5c50aec71c75c59232b3ede4"),
  "angle_a" : NumberDecimal("53.13010235415597870314438744090660"),
  "angle_b" : NumberDecimal("36.86989764584402129685561255909341"),
  "angle_c" : NumberDecimal("90"),
  "angle_a_rad" : NumberDecimal("0.9272952180016122324285124629224290"),
  "angle_b_rad" : NumberDecimal("0.6435011087932843868028092287173227"),
  "angle_c_rad" : NumberDecimal("1.570796326794896619231321691639752")
}

Since angle_a, angle_b, and angle_c are stored as 128-bit decimals, the output of $degreesToRadians is a 128-bit decimal.由于angle_a、angle_b和angle_c存储为128位小数，因此$degreesToRadians的输出为128位小数。