Visualize connected components in Neo4j

Question

I can find the highest densely connected component in the graph using the code below:

CALL algo.unionFind.stream('', ':pnHours', {})
YIELD nodeId,setId
// groupBy setId, storing all node ids of the same set id into a list
MATCH (node) where id(node) = nodeId
WITH setId, collect(node) as nodes
// order by the size of nodes list descending
ORDER BY size(nodes) DESC
LIMIT 1 // limiting to 3
RETURN nodes;

But it does not help me visualize the topmost densely connected component (sub-graph) because the output graph it emits are disjoint nodes. Is it possible to visualize the densely connected component. If yes, then how

Answer 1

I tried this query but I am getting different the result.

I haven't used these algorithms and I don't know much about it, but I think you added an extra character (colon) in the query.

Can you check with pnHours instead of :pnHours.

I remove colon(:) from the query and I am getting the proper result (also I am able to get the relationships as well because Neo4j browser fetches it although it's not specified in the query).

If you still don't get check the following query:

CALL algo.unionFind.stream('', 'pnHours', {})
YIELD nodeId,setId
// groupBy setId, storing all node ids of the same set id into a list
MATCH (node) where id(node) = nodeId
WITH setId, collect(node) as nodes
// order by the size of nodes list descending
ORDER BY size(nodes) DESC
LIMIT 1 // limiting to 3
WITH nodes
UNWIND nodes AS node
MATCH (node)-[r:pnHours]-()
RETURN node,r;

Answer 2

If you want to visualize then in Neo4j browser then use:

CALL algo.unionFind.stream('', ':pnHours', {})
YIELD nodeId,setId
// groupBy setId, storing all node ids of the same set id into a list
MATCH p=(node)-->() where id(node) = nodeId
WITH setId, collect(p) as paths
// order by the size of nodes list descending
ORDER BY size(paths) DESC
LIMIT 1 // limiting to 3
// Maybe you need to unwind paths to be able to visualize in Neo4j browser
RETURN paths;

It is not the most optimized query but should do just fine on small datasets.

Answer 3

The following query should return all the single-step paths in the largest pnHours-connected component (i.e., the one having the most nodes). It only gets the paths for the largest component.

CALL algo.unionFind.stream(null, 'pnHours', {}) YIELD nodeId, setId
WITH setId, COLLECT(nodeId) as nodeIds
ORDER BY SIZE(nodeIds) DESC
LIMIT 1
UNWIND nodeIds AS nodeId
MATCH path = (n)-[:pnHours]->()
WHERE ID(n) = nodeId
RETURN path

The neo4j browser's Graph visualization of the results will show all the nodes in the component and their relationships.