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Graph Data Science

Union-Find

The algorithm underlying Weakly Connected Components. It holds each node in a set, and merges two sets whenever a relationship joins them.

Example

Four people, and two relationships read one after the other.

Each person starts in a set of their own, four sets in all. Reading the relationship between Ava and Ben merges their two sets into one. Reading the relationship between Cleo and Dan merges theirs. Nothing joins one pair to the other, so two sets are left.

cypher
CALL gds.wcc.stream('people')
YIELD nodeId, componentId
RETURN gds.util.asNode(nodeId).name AS person, componentId

Ava and Ben come back with one componentId, Cleo and Dan with another.

Lessons that use this term

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One lesson uses this term.

Graph Data Science in Practice3 mentions

  • Degree Centrality & WCCCommunity Detection for Frauddegree centrality with different orientations and weights Explain the Union-Find algorithm underlying WCC Configure WCC with thresholds, seeding, and performance optimizations Choose between3 mentions

Related terms

weakly connected components
Groups of nodes in which every node is reachable from every other, once relationship direction is ignored. The GDS algorithm that finds them takes the same name.1 shared lesson
modularity
A score for how much more densely connected the nodes within a group are than they would be by chance.1 shared lesson
centrality
How important a node is within a graph. Each centrality algorithm defines importance differently.1 shared lesson
undirected relationship
A relationship with no direction. Neo4j GDS represents them as parallel relationships in opposite directions.1 shared lesson
degree centrality
A score for each node equal to its number of outgoing relationships.1 shared lesson
Louvain algorithm
A community detection algorithm that repeatedly merges nodes into groups for as long as merging raises modularity.1 shared lesson
bipartite graph
A graph with two kinds of node, where every relationship joins one kind to the other and never two of the same kind.1 shared lesson
path
A sequence of nodes joined by relationships.1 shared lesson

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