# Aggregation Pipeline Operators

The aggregation pipeline operators construct expressions for use in the aggregation pipeline stages. The following are the list of Aggregation Pipeline Operators.

## Arithmetic Expression Operators

It is used to perform arithmetic operations on numbers. Some arithmetic expression also supports data arithmetic.

### \$abs

The abs operator returns the absolute value of a number.

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Example:

It adds two or more numbers and a date. If one of the arguments is a date, then the date treats the other argument as milliseconds to add to the date.

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### \$ceil

The ceil operator returns the smallest integer that is greater than or equal to the specified number.

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### \$divide

It divides one or more numbers by another and returns the result.

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### \$exp

The exp operator is used to raise Euler's number to the specified exponent and returns the result.

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### \$floor

The floor operator returns the greatest integer less than or equal to the specified number.

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### \$ln

The ln operator calculates the natural logarithm of a number and returns the result as a double.

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### \$log

The log operator calculates the log of a number for the specified base and returns the result as double.

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### \$log10

The log10 operator calculates the log base 10 of a number and returns the result as a double.

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### \$mod

The mod operator divides one number with another and returns the remainder.

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### \$multiply

The multiply operator gives the product of two or more numbers.

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### \$pow

The pow operator raises the number to the given exponent and returns the result.

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### \$round

The round operator rounds a number to a whole integer or a specified decimal place.

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### \$sqrt

The sqrt operator returns the square root of a positive number as double.

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### \$subtract

The subtract operator subtracts two or more numbers to return the difference of the number.

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### \$trunc

The trunc command deletes the data from the specified decimal place.

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## Array Expression Operator

### \$arrayElemAt

It returns the element at the specified array index.

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### \$arrayToObject

The arrayToObject operator converts an array into a single document.

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### \$concatArrays

The concatArrays operator joins the array to return the concatenated array.

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### \$filter

The filter operator selects a subset of an array to return the result based on the specified condition.

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### \$in

The in operator returns a boolean indicating that the specified value is in the array or not.

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### \$indexOfArray

The indexOfArray operator searches the array for the occurrence of a specified value and returns the array index of the first occurrence.

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### \$isArray

It determines and returns a Boolean value if the operand is an Array.

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### \$map

The map operator attaches value to each item in an array and returns an array with the applied result.

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### \$objectToArray

This operator converts a document to an array.

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### \$range

The range operator returns an array whose elements are a generated sequence of numbers.

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### \$reduce

The reduce operator applies an expression to each element in an array and combines them into a single value.

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### \$reverseArray

It returns an array with the element in reverse order.

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### \$size

The size operator counts and returns the total number of items in an array.

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### \$slice

The slice operator results in a subset of an array.

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### \$zip

The zip operator transposes an array so that the first element of the output array would be an array containing the first element of the first input array.

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