[igraph] as_clustering() error

[xiao wu]

I am new to igraph and use python igraph 0.6.5 in ubuntu python 2.7.

I have my own pajek file I loaded into python, and ran community detection algorithm and got the following dendrogram

>>> print(dendrogram)

Dendrogram, 1335 elements, 314 merges

But when I tried to run as_clusting, I got the following error:

>>> clusters = dendrogram.as_clustering()

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

  File "/usr/lib/python2.7/dist-packages/igraph/clustering.py", line 959, in as_clustering

    num_elts - n)

igraph._igraph.InternalError: Error at community.c:767: `steps' to big or `merges' matrix too short, Invalid value

How do I debug from here? My pajek file's Vertices are not continuous. Would that create a problem?

Thanks,

Xiao