Hi there, I have recently answered your question on Stack Overflow, but I'm copying my response here as well for the record:
"When an algorithm in igraph produces a `VertexDendrogram`, it may optionally produce a "hint" as well that tells us where to cut the dendrogram (i.e. after how many merges) to obtain a `VertexClustering` that is in some sense optimal. For instance, the `VertexDendrogram` produced by `community_fastgreedy()` proposes that the dendrogram should be cut at the point where the modularity is maximized. Running `as_clustering()` on a `VertexDendrogram` simply uses the hint produced by the clustering algorithm to flatten the dendrogram into a clustering, but you may override this by specifying the desired number of clusters as an argument to `as_clustering()`." -- T. On 2 Jul 2013, at 18:53, "Durante, Joseph [USA]" <[email protected]> wrote: > Hi there, > > I’m a relatively new user of iGraph and need some help with understanding a > function in iGraph run in Python. > > Using iGraph's community detection function community_fastgreedy(), I got a > VertexDendrogram object, let's call it V. Then using V.as_clustering() I got > a VertexClustering object from the dendrogram. I know that the communities > are clustered so that modularity is maximized, but I think the dendogram > object keeps merging all the way, so it's tough to see the communities on the > dendrogram. > > My question is: How does the output for the V.as_clustering() correspond to > distance between the communities in the dendrogram? > > In other words, The communities each come with a representative number ( > Community [0], Community [2] for example), so how does the that number > correspond to position on the dendrogram? Are community 0 and Community 1 > adjacent to each other when the dendrogram is merged up to the level that > maximizes modularity, and is community 12 farther from community 0 than 3 is? > > If not, then how is the order (the numbers for each community) of the output > decided by the as_clustering function? > > Thanks in advance. > > -Joe > > _______________________________________________ > igraph-help mailing list > [email protected] > https://lists.nongnu.org/mailman/listinfo/igraph-help _______________________________________________ igraph-help mailing list [email protected] https://lists.nongnu.org/mailman/listinfo/igraph-help
