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[igraph] Differences in Usage of get.diameter for R Package

From: Lorenzo Isella
Subject: [igraph] Differences in Usage of get.diameter for R Package
Date: Mon, 14 Dec 2009 19:37:34 +0100

Dear All,
I am running igraph (R bindings) on two different 64-bit machines (one
running Ubuntu 9.10 and igraph for R compiled from source and the
other one Debian testing and igraph installed as a binary from
deb http://debian.cran.r-project.org/cran2deb/debian-amd64/ testing/ ).

I realized that I was getting very different results in the
calculation of the graph diameter for the same (weighted) graph on my
machines and I had a look at the help.
The package installed as a binary has the following usage of get.diameter:

Diameter of a graph


     The diameter of a graph is the length of the longest geodesic.


     diameter(graph, directed = TRUE, unconnected = TRUE, weights = NULL)
     get.diameter (graph, directed = TRUE, unconnected = TRUE, weights = NULL)
     farthest.nodes (graph, directed = TRUE, unconnected = TRUE,
weights = NULL)


   graph: The graph to analyze.

directed: Logical, whether directed or undirected paths are to be
          considered. This is ignored for undirected graphs.

unconnected: Logical, what to do if the graph is unconnected. If FALSE,
          the function will return the largest possible diameter which
          is the number of vertices. If TRUE, the diameters of the
          connected components will be calculated and the largest one
          will be returned.

 weights: Optional positive weight vector for calculating weighted
          distances. If the graph has a ‘weight’ edge attribute, then
          this is used by default

so, it calculates the diameter for a weighted graph, whereas the
package installed from source has the same documentation as what I
find online


which does not mention the weight at all.
Which one is the 'correct' get.diameter? And also, given a weighted
graph and an R library which uses the weight when calculating the
diameter, how do I tell it to calculate the topological, unweighted
Kind Regards


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