问题
I am calculating a set of paths using apoc.algo.dijkstra. My goal is to assign a rank to each of the suggested paths. Important is all the weights among nodes are floats. Cypher code:
...
WITH origin, target CALL apoc.algo.dijkstra(origin, target, 'link',
'Weight') yield path as path, weight as weight
...
what I have now:
Path 1 - Weight: 1.2344332423
Path 2 - Weight: 0.8432423321
Path 3 - Weight: 0.9144331653
Something what I need is:
rank: 1, weight: 1.2344332423
rank: 2, weight: 0.9144331653
rank: 3, weight: 0.8432423321
How can I do this inside the Cypher query.
Note: I already read the post related to calculating the rank, but it doesn't suit to my specific case.
How to calculate a rank in Neo4j
Thank you!
Additional info: I am trying now to merge the ranking and wight values with origin and path. I could succesully do this for origin:
CALL
apoc.load.json("file:///.../input.json") YIELD value
UNWIND value.origin AS orig
MATCH(origin:concept{name:orig.label}) WITH value, collect(origin) as
origins
UNWIND value.target AS tar MATCH(target:concept{name:tar.label})
UNWIND origins AS origin WITH origin, target
CALL apoc.algo.dijkstra(origin, target, 'link', 'Weight') yield path as
path, weight as weight
WITH origin, path, weight ORDER BY weight ASC WITH {origin: origin, weight:
collect(weight)} AS SuggestionForOrigin UNWIND [r in range(1,
SIZE(SuggestionForOrigin.weight)) | {origin: SuggestionForOrigin.origin,
rank:r, weight: SuggestionForOrigin.weight[r-1]}] AS suggestion RETURN
suggestion
Then I get the following result (which is satisfying for me):
{"origin": {"name": "A","type": "string"},"rank": 1,"weight": 0.0}
{"origin": {"name": "A","type": "string"},"rank": 2,"weight":
0.6180339887498948}
{"origin": {"name": "P1","type": "string"},"rank": 1,"weight":
0.6180339887498948}
{"origin": {"name": "P1","type": "string"},"rank": 2,"weight":
1.2360679774997896}
But when I am trying to merge "path" parameter, I am getting into trouble. I think, I overcompensate the things. Something what I would like to achieve is:
{"origin": {....}, "path": {...}, "rank": 1,"weight": 0.0}
And this need to be related to a particular origin node, if I have 3 paths suggestions for the first origin, they need to be combined together. What I#ve tried, but it doesn't work as I want is:
...
CALL apoc.algo.dijkstra(origin, target, 'link', 'Weight') yield path as
path, weight
WITH {origin: origin, path: collect(path), weight: collect(weight)} AS
SuggestionForOrigin
UNWIND [r in range(1, SIZE(SuggestionForOrigin.weight)) | {rank:r, weight:
SuggestionForOrigin.weight[r-1], path: SuggestionForOrigin}] AS suggestion
WITH {origin: SuggestionForOrigin.origin, suggestions: collect(suggestion)
[0..3]} AS output
RETURN output
I would appreciate, if you could help.
回答1:
This may work for you:
...
WITH origin, target
CALL apoc.algo.dijkstra(origin, target, 'link', 'Weight') YIELD weight
WITH weight
ORDER BY weight DESC
WITH COLLECT(weight) AS ws
UNWIND [r IN RANGE(1, SIZE(ws)) | {rank:r, weight: ws[r-1]}] AS res
RETURN res;
The result (assuming your sample data) would look like this:
╒════════════════════════════════╕
│"res" │
╞════════════════════════════════╡
│{"rank":1,"weight":1.2344332423}│
├────────────────────────────────┤
│{"rank":2,"weight":0.9144331653}│
├────────────────────────────────┤
│{"rank":3,"weight":0.8432423321}│
└────────────────────────────────┘
[UPDATE]
If you want to also return the origin and path (and rank by ascending weight), see this answer.
来源：https://stackoverflow.com/questions/56745666/how-to-calculate-rank-for-float-values-in-neo4j