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$atan (aggregation)

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New in version 4.2.

Returns the inverse tangent (arc tangent) of a value.

$atan has the following syntax:

{ $atan: <expression> }

$atan takes any valid expression that resolves to a number.

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

By default $atan returns values as a double. $atan can also return values as a 128-bit decimal as long as the <expression> resolves to a 128-bit decimal value.

For more information on expressions, see Expressions.

If the argument resolves to a value of null or refers to a field that is missing, $atan returns null. If the argument resolves to NaN, $tan returns NaN.

{ $atan: NaN }
{ $atan: null }

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