This paper provides a theoretical explanation on the clustering aspect of
nonnegative matrix factorization (NMF). We prove that even without imposing
orthogonality or sparsity constraint on the basis and/or coefficient matrix,
NMF still can give clustering results, thus providing a theoretical support for
the works of Xu et al. [1] and Kim et al. [2], where the authors showed the
superiority of the standard NMF as a clustering method.
We describe a clustering method for labeled link network (semantic graph)
that can be used to group important nodes (highly connected nodes) with their
relevant link's labels by using PARAFAC tensor decomposition. In this kind of
network, the adjacency matrix can not be used to fully describe all information
about the network structure. We have to expand the matrix into 3-way adjacency
tensor, so that not only the information about to which nodes a node connects
to but by which link's labels is also included.
We present a new method to accelerate the HITS algorithm by exploiting
hyperlink structure of the web graph. The proposed algorithm extends the idea
of authority and hub scores from HITS by introducing two diagonal matrices
which contain constants that act as weights to make authority pages more
authoritative and hub pages more hubby. This method works because in the web
graph good authorities are pointed to by good hubs and good hubs point to good
authorities. Consequently, these pages will collect their scores faster under
the proposed algorithm than under the standard HITS.