cardinality - The number of unique elements in an array

Returns the number of unique elements in the array

Syntax

Like many functions in DataPrime, cardinality supports two notations, function and method notation. These interchangeable forms allow flexibility in how you structure expressions.

Function notation

cardinality(array: array<T>): number

Method notation

array: array<T>.cardinality(): number

Arguments

Name	Type	Required	Description
array	array of type T	true	T must be either `string`, `bool`, `number`, `interval`, `timestamp`, `regexp` or `enum`

Example - Detecting new IP addresses

Consider the following document:

{
    "active_ips": ["123.45.32.1", "111.230.76.5", "9.8.7.1"]
}

Assume that we have a closed system, and we know that we should only have, at most, five users. Any more is cause for concern. We can use cardinality to count the number of unique IP addresses in our array.

Function notation

create unique_ip_count from cardinality(active_ips)

Method notation

create unique_ip_count from active_ips.cardinality()

This will result in the following document:

{
    "active_ips": ["123.45.32.1", "111.230.76.5", "9.8.7.1"],
    "unique_ip_count": 3
}

This can now power alerts, reports and more.

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