$log (aggregation)
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Definition
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$log
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New in version 3.2.
Calculates the log of a number in the specified base and returns the result as a double.
$log
has the following syntax:The
<number>
expression can be any valid expression as long as it resolves to a non-negative number.The
<base>
expression can be any valid expression as long as it resolves to a positive number greater than1
.For more information on expressions, see Expressions.
Behavior
If either argument resolves to a value of null
or refers to a field that is missing, $log
returns null
. If either argument resolves to NaN
, $log
returns NaN
.
Example | Results |
---|---|
{ $log: [ 100, 10 ] } |
2 |
{ $log: [ 100, Math.E ] } where Math.E is a JavaScript representation for e. |
4.605170185988092 |