sim.jaccard

Description

Computes the Jaccard similarity coefficient between two sets (lists). The Jaccard index measures the similarity between two sets by dividing the size of their intersection by the size of their union. It returns a value between 0 (no similarity) and 1 (identical sets).

Syntax 

flex.sim.jaccard(list1, list2)

Parameters

| Parameter | Type | Required | Description | |———–|——|———-|————-| | list1 | list | Yes | The first list to compare | | list2 | list | Yes | The second list to compare |

Returns

Type: number (float)

A value between 0 and 1 representing the Jaccard similarity coefficient:

  • 1.0 indicates identical sets
  • 0.0 indicates no common elements
  • Returns null for invalid inputs

Examples

Example 1: Basic Set Similarity 

// Compare two tag lists
RETURN flex.sim.jaccard(['tag1', 'tag2', 'tag3'], ['tag2', 'tag3', 'tag4']) AS similarity

Output:

similarity
----------
0.5

(2 common elements / 4 total unique elements = 0.5)

Example 2: Finding Similar Documents by Tags 

// Find documents with similar tags to a reference document
MATCH (ref:Document {id: 'doc123'})
MATCH (other:Document)
WHERE other.id <> ref.id
WITH ref, other, flex.sim.jaccard(ref.tags, other.tags) AS similarity
WHERE similarity > 0.3
RETURN other.title, similarity
ORDER BY similarity DESC
LIMIT 10

Example 3: User Interest Matching 

// Find users with similar interests
MATCH (u1:User {id: $userId})
MATCH (u2:User)
WHERE u1 <> u2
WITH u1, u2, flex.sim.jaccard(u1.interests, u2.interests) AS match_score
WHERE match_score > 0.5
RETURN u2.name, u2.interests, match_score
ORDER BY match_score DESC

Notes

  • Treats input lists as sets (duplicates within each list don’t affect the result)
  • Returns null if either input is not an array
  • Order of elements doesn’t matter
  • Works with any comparable data types (strings, numbers, etc.)
  • Ideal for comparing categorical attributes, tags, or interest lists

See Also