[R] Finding all triangles in a graph

Albyn Jones jones at reed.edu
Tue Dec 27 20:38:07 CET 2011


The general problem of finding subgraphs with a given structure ("motifs")
is hard (ie computationally expensive).  There is some literature...

have you looked at the package igraph, function graph.motifs()?


Quoting Taral <taralx at gmail.com>:

> I have the adjacency matrix of a graph. I'm trying to find all
> triangles (embeddings of C_3). This doesn't work:
> index = function(l) seq(l)[l]
> pairs = do.call(rbind, lapply(seq(nrow(adj)), function(x) cbind(x,
> index(adj[x,]))))
> triangles = do.call(rbind, apply(pairs, 1, function(x) cbind(x,
> index(adj[x[1],] & adj[x[2],]))))
> I'm absolutely certain I've gone down the wrong path here. O great R
> gurus, your guidance would be most welcome.
> --
> Taral <taralx at gmail.com>
> "Please let me know if there's any further trouble I can give you."
>     -- Unknown
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