I haven't read the papers once again, but in my opinion a disconnected
motif doesn't really make sense. Consider a disconnected motif that
consists of a fully connected triangle and an additional isolated
vertex, and then take a graph that contains one triangle and one
million isolated vertices. Does that really mean that this "motif"
appears one million times in the graph? Is that a significant finding?
If I added an additional one million totally unrelated vertices to the
graph, does that make the motif appear twice as frequently?

Anyway, if you want to search for disconnected patterns in a graph,
you can still use count_subgaph_isomorphisms() with method="lad" and
induced=TRUE; see:


It will be much slower, though -- searching for connected motifs is
much easier if the average degree of a vertex is low.


On Fri, Oct 14, 2016 at 8:59 AM, Manuel Zetina-Rejon <mjzet...@gmail.com> wrote:
> Hi Guys!
> This is probably a basic question, but I don’t find the clear criteria or 
> reference, why in igraph help, you mention that unconnected subgraphs (of x 
> isomorphic class) are not considered motifs? For that reason, motifs() is NA 
> for unconnected subgraphs. It is also not clear if you mean strongly or 
> weakly connected subgraphs
> According to Milo et al. (2002) and Shen-Orr et al. (2002) motifs are not 
> necessarily connected, even in directed graphs.
> Thank you for your opinions
> Manuel
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