# Question about: How can I calculate edges

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### #1 Davide Posted 31 March 2010 - 05:14 AM

Davide

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Hi,

I have a question:

Data: I have a road network (vector) with several nodes on it

I want to calculate the distance between two nodes. I want to use a mathematical formula "closeness centrality"

When I use the functions in ArcMap => "Math" - in arc Toolbox, I would have to transform it into raster, but I think this makes no sense. Is it possible to calculate it with vector?

It's very confusing I know. But maybe there is someone who could help me!

best regards,

David

### #2 Kartograph Posted 31 March 2010 - 07:51 AM

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Do you want euclidian distance or number of "hops" in the network?

### #3 Leeroy Posted 31 March 2010 - 02:33 PM

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Do you want euclidian distance or number of "hops" in the network?

I want to define centrality of the nodes, which one is the central one, second thrid, ....

Therefor I want to use several methods - one possibility i have already used is: OD Cost Matrix.

But in my project I used as I wrote before a mathematical formula => Closeness Centrality

I do not really know if I have to use the eurlidean distance, I think the network distance would be better.
Or not?!

best regards
David

Hallo Danke fürs zurückschreiben.... Ich komme eigentlich aus Österreich, deshalb schreibe ich das auch noch in deutsch...

Also ich habe wie gesagt ein Straßennetzwerk auf dem 18 (in meinem Fall) Fußballmannschaften eingetragen sind.

Ich möchte nun wissen welcher dieser Mannschaften die zentralste ist. Es gibt dazu verschiedene Zentralitätsindizes u.a die "Closeness Zentralität". Ich habe einen Link angefügt damit du weißt wie die Formel ausssieht.

http://www.informati...um/indizes.html

Ich möchte diese Formel, wenn möglich mittels ModelBuilder oder wie auch immer Umsetzen. Eine andere Möglichkeit die ich bereits verwendet habe ist die OD Cost Matrix, war ja auch nicht schwer, einfach in das Formular einsetzen.

Aber nun möchte ich auch jene Variante ausprobieren, die ich in der Arbeit angegeben habe. Ich habe wie gesagt ein Vektor basiertes Netzwerk. Und die mathematischen Tools funktionieren nur mit Raster, aber Umwandeln macht keinen Sinn!

Weißt du wie ich das meine?!
Ich wäre für jede Hilfe sehr dankbar!

Vg David

### #4 Kartograph Posted 01 April 2010 - 06:26 AM

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The "Math" [actually it´s "map math" what they mean with that IIRC] in ArcGIS is always about rasters. Regarding your centrality problem, I think you must first decide upon what measure you really want. The closeness centrality, if calculated in, say, a city, will consider all nodes. That would be every intersection etc. for a typical street network. This would tell you something about the centrality of the teams within the area, but not within a graph between them. If the Teams are the nodes, you better take a low-fi graph analyzer.

The first case would need to choose a vertex and calculate the shortest route towards all other nodes, that should work in the Network Analyst, don´t know how the performance is though, for your network. I would do the loop for all nodes and the summation of the "solve" output with a (python) script coupled to the model builder.

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