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$atanh（表达式操作符）

$atanh

返回某个值的反双曲正切（双曲弧正切）值。

$atanh 通过以下语法实现：

{ $atanh: <expression> }

$atanh takes any valid expression that resolves to a number between -1 and 1, e.g. -1 <= value <= 1.

$atanh returns values in radians. Use $radiansToDegrees operator to convert the output value from radians to degrees.

默认下，$atanh 128 $atanh返回double<expression> 128形式的值。只要解析为位十进制值，也可以返回位十进制值。

有关表达式的更多信息，请参阅表达式。

行为

`null`、`NaN` 和`+/- Infinity`

If the argument resolves to a value of null or refers to a field that is missing, $atanh returns null. If the argument resolves to NaN, $atanh returns NaN. If the argument resolves to negative or positive infinity, $atanh throws an error. If the argument resolves to +1 or -1, $atanh returns Infinity and -Infinity respectively.

例子

结果

{ $atanh: NaN }

NaN

{ $atanh: null }

null

{ $atanh: 1 }

Infinity

{ $atanh: -1}

-Infinity

{ $atanh : Infinity}

{ $atanh : -Infinity }

抛出一条类似以下格式化输出的错误消息：

"errmsg" :
  "Failed to optimize pipeline :: caused by :: cannot
  apply $atanh to -inf, value must in (-inf,inf)"

例子

trigonometry 集合包含一个文档，该文档沿 2-D 图的 x 轴存储值：

{
  "_id" : ObjectId("5c50782193f833234ba90d85"),
  "x-coordinate" : Decimal128("0.5")
}

The following aggregation operation uses the $atanh expression to calculate inverse hyperbolic tangent of x-coordinate and add it to the input document using the $addFields pipeline stage.

db.trigonometry.aggregate([
  {
    $addFields : {
      "y-coordinate" : {
        $radiansToDegrees : { $atanh : "$x-coordinate" }
      }
    }
  }
])

The $radiansToDegrees expression converts the radian value returned by $atanh to the equivalent value in degrees.

该命令返回以下输出：

{
  "_id" : ObjectId("5c50782193f833234ba90d85"),
  "x-coordinate" : Decimal128("0.5"),
  "y-coordinate" : Decimal128("31.47292373094538001977241539068589")
}

由于x-coordinate 128存储为位十进制数，因此$atanh 的输出为128 位十进制数。

trigonometry 集合包含一个文档，该文档沿 2-D 图的 x 轴存储值：

{
  "_id" : ObjectId("5c50782193f833234ba90d85"),
  "x-coordinate" : Decimal128("0.5")
}

The following aggregation operation uses the $atanh expression to calculate inverse hyperbolic tangent of x-coordinate and add it to the input document using the $addFields pipeline stage.

db.trigonometry.aggregate([
  {
    $addFields : {
      "y-coordinate" : {
        $atanh : "$x-coordinate"
      }
    }
  }
])

该命令返回以下输出：

{
  "_id" : ObjectId("5c50782193f833234ba90d85"),
  "x-coordinate" : Decimal128("0.5"),
  "y-coordinate" : Decimal128("0.5493061443340548456976226184612628")
}

由于x-coordinate 128存储为位十进制数，因此$asin 的输出为128 位十进制数。

$atanh（表达式操作符）

行为

null、NaN 和+/- Infinity

例子

`null`、`NaN` 和`+/- Infinity`