neo4j aggregate function by distance - neo4j

Question

I want to have some aggregated statistics by distance from root. For example,
(A)-[value:20]->(B)-[value:40]->(C)
(A)-[value:0]->(D)-[value:20]->(E)
CREATE (:firm {name:'A'}), (:firm {name:'B'}), (:firm {name:'C'}), (:firm {name:'D'}), (:firm {name:'E'});
MATCH (a:firm {name:'A'}), (b:firm {name:'B'}), (c:firm {name:'C'}), (d:firm {name:'D'}), (e:firm {name:'E'})
CREATE (a)-[:REL {value: 20}]->(b)->[:REL {value: 40}]->(c),
(a)-[:REL {value: 0}]->(d)->[:REL {value: 20}]->(e);
I want to get the average value of A's immediate neighbors and that of the 2nd layer neighbors, i.e.,
+-------------------+
| distance | avg |
+-------------------+
| 1 | 10 |
| 2 | 30 |
+-------------------+
How should I do it? I have tried the following
MATCH p=(n:NODE {name:'A'})-[r:REL*1..2]->(n:NODE)
RETURN length(p), sum(r:value);
But I am not sure how to operate on the variable-length path r.
Similarly, is it possible to get the cumulative value? i.e.,
+-------------------+
| name | cum |
+-------------------+
| B | 20 |
| C | 60 |
| D | 0 |
| E | 20 |
+-------------------+

Answer 1

The query below solves the first problem. Please note that it also solves the case where paths are not of equal length. I added (E)-[REL {value:99}]->(F)
MATCH path=(:firm {name:'A'})-[:REL*]->(leaf:firm)
WHERE NOT (leaf)-[:REL]->(:firm)
WITH COLLECT(path) AS paths, max(length(path)) AS longest
UNWIND RANGE(1,longest) AS depth
WITH depth,
REDUCE(sum=0, path IN [p IN paths WHERE length(p) >= depth] |
sum
+ relationships(path)[depth-1].value
) AS sumAtDepth,
SIZE([p IN paths WHERE length(p) >= depth]) AS countAtDepth
RETURN depth, sumAtDepth, countAtDepth, sumAtDepth/countAtDepth AS avgAtDepth
returning
╒═══════╤════════════╤══════════════╤════════════╕
│"depth"│"sumAtDepth"│"countAtDepth"│"avgAtDepth"│
╞═══════╪════════════╪══════════════╪════════════╡
│1 │20 │2 │10 │
├───────┼────────────┼──────────────┼────────────┤
│2 │60 │2 │30 │
├───────┼────────────┼──────────────┼────────────┤
│3 │99 │1 │99 │
└───────┴────────────┴──────────────┴────────────┘
The second question can be answered as follows:
MATCH (root:firm {name:'A'})
MATCH (descendant:firm) WHERE EXISTS((root)-[:REL*]->(descendant))
WITH root,descendant
WITH descendant,
REDUCE(sum=0,rel IN relationships([(descendant)<-[:REL*]-(root)][0][0]) |
sum + rel.value
) AS cumulative
RETURN descendant.name,cumulative ORDER BY descendant.name
returning
╒═════════════════╤════════════╕
│"descendant.name"│"cumulative"│
╞═════════════════╪════════════╡
│"B" │20 │
├─────────────────┼────────────┤
│"C" │60 │
├─────────────────┼────────────┤
│"D" │0 │
├─────────────────┼────────────┤
│"E" │20 │
├─────────────────┼────────────┤
│"F" │119 │
└─────────────────┴────────────┘

Answer 2

may I suggest your try it with a reduce function, you can retro fit it your code
// Match something name or distance..
MATCH
// If you have a condition put in here
// WHERE A<>B AND n.name = m.name
// WITH filterItems, collect(m) AS myItems
// Reduce will help sum/aggregate entire you are looking for
RETURN reduce( sum=0, x IN myItems | sum+x.cost )
LIMIT 10;