Query for nodes, degree,in degree, outdegree

[Koen]

hi, sorry for asking so much questions .. but trying to get my personal "coin" dropping in my head for cypher ..

for example how can i query all nodes in a graph and create a list of all nodes and for each node the name,degree,indegree and outdegree ?

i have managed to create seperate queries doing part of this (so all nodes with total degree) .. or all nodes with in degree .. but somehow  i cannot succeed in (at the end) outputting this in one combined result

i guess the WITH has to come in play maybe ?

reesult should looke like

node    degree   indegree   outdegree
a          5      3    2
b          7      1     6
c          3       2    1
d          1       0     1

thx koen

[Koen Kleingeld]

wow . i solved my own question...

start home=node(*)
match home--()
WITH home,count(*) as degree
match home-->()
WITH home,degree,count(*) as outdegree
match home<--()
return home.name,degree,outdegree,count(*) as indegree
order by home.name

is this the most "minimal" query for my goal ?

thx Koen

2013/6/30 Koen <kdwykl...@gmail.com>

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Groeten / Best Regards,

Koen

[Peter Neubauer]

Cool,

steep learning curve Koen!

/peter

Cheers,

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[Michael Hunger]

You can also aggregate the degree from both:

start home=node(*)

match home-->()
WITH home,degree,count(*) as outdegree
match home<--()

return home.name, count(*) + outdegree AS degree, outdegree, count(*) AS indegree

order by home.name

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[Koen Kleingeld]

hi thx, thats great... i was in the process of removing the last WITH myself but could not succeed in calculating the remaining degree.. this will help

is it actually so that for every WITH you add the whole graph is traversed again according to what has been defined in the very first "start"  command ?   so when you have a "start bla=node(*)" the whole graph is traversed again for every new WITH ?

reg koen

2013/7/1 Michael Hunger <michael...@neotechnology.com>

[Michael Hunger]

No, WITH is like a unix pipe

It specify what is forwarded to the next part but keeps the same cardinality (except if you aggregate or filter with WHERE)

The traversal of the graph comes from MATCH

Michael


Sent from mobile device

[Koen Kleingeld]

thx, actually the algorithm does not work since it drops the beginning and end nodes of the graph..  you only get results for the nodes that are not at the edges ..

any ideas to cover all nodes ? thx

2013/7/1 Michael Hunger <michael...@neopersistence.com>

[Michael Hunger]

What do you mean?

Do you have an example?

E.g set one up in console.neo4j.org and share it with the "share" button.

Michael

[Koen]

hi, see 2 pictures

Op zondag 30 juni 2013 16:30:13 UTC+2 schreef Koen het volgende:

[Koen Kleingeld]

Hi, if you run the query against the demo setup in the neo console you can see it leaves out 3 nodes that are located at the edges (or have only incoming edges)   - (architect / 0 and trinity)

START home=node(*)
MATCH home-->()
WITH home,count(*) AS outdegree
MATCH home<--()
RETURN home.name, count(*)+ outdegree AS degree, outdegree, count(*) AS indegree
ORDER BY home.name

.. i guess we have to start matching for "degree" .. so   match home--()

but when aggregating you loose the nodes that have only one direction as connection..

reg koen

[Michael Hunger]

I don't see what's wrong with the output?

Oh you mean that some nodes don't show up because they didn't have in degree or out-degree? That's because they are filtered out as non-matching.

you can also use path-expressions as expressions to compute that.

start n=node(*)

WITH n,length(n-->()) as outdegree, length(n<--()) as indegree

return n, outdegree, indegree, outdegree+indegree AS degree

Michael

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<queryandresults.jpg><rbacsamplegraph.jpg>

[Koen Kleingeld]

hi, thx,  yes thats what i mean... i was not sure how to retain the first aggregation result ...  

but at the end all is possible it seems !!  hopefully i will reach this cypher knowledge level some time ... 

this algoritm works out fine

reg koen

2013/7/2 Michael Hunger <michael...@neotechnology.com>

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