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Two Modified Sparse Subspace Clustering
XIAOYAN WANG
North University of China
School of Information
and Communication Engineering
Xueyuan Road 3, 030051 Taiyuan
CHINA
xywang00@126.com
CAIXIA ZHANG
North University of China
School of Science
Xueyuan Road 3, 030051 Taiyuan
CHINA
18535152702@163.com
YANPING BAI
North University of China
School of Science
Xueyuan Road 3, 030051 Taiyuan
CHINA
baiyp666@163.com
Abstract: Sparse Subspace Clustering constructs a sparse similarity graph by using the coefficient of sparse rep-
resentation to subspace clustering. Based on sparse representation techniques, the algorithm gets the sparse coef-
ficient by using l
1
-minimization and gets clusters’ data by spectral clustering algorithm. The spectral clustering
algorithm depends on k-means algorithm for data clustering, while k-means algorithm is sensitive to the choice
of initial starting conditions and it needs iterations. In order to avoid the drawbacks of k-means algorithm, we
propose two modified Sparse Subspace Clustering algorithm, then the results are not be affected by the centers or
the iterations. In one of the method, we get the clusters by comparing the positions of nonzero elements in the
sparse adjacent matrix of similarity graph and the eigenvector. And in the second method, we use SOM algorithm
instead of k-means algorithm. The experiment results show our proposed algorithm outperforms the initial Sparse
Subspace Clustering.
Key–Words: subspace clustering,spectral clustering,k-means,SOM
1 Introduction
Clustering is one of classic problems in pattern
recognition, image processing, machine learning and
statistics [1, 2], which aims to partition a collection
of patterns into disjoint clusters, such that patterns in
the same cluster are similar, however patterns belong
to two different clusters are dissimilar. In many areas
of machine learning, image processing and computer
vision applications require processing and represen-
tation of high-dimensional data. In fact, these high-
dimensional data often can be represented by a low-
dimensional subspace. For example, face images of
a object under varying illumination conditions can be
well approximated by 9-dimensional linear subspace
[3]. Subspace clustering [4] separates data according
to their underlying subspaces and is applied to image
processing [5] and computer vision [6].
Recently, Elhamifar and Vidal [7, 8] have intro-
duced an approach which constructed a sparse similar-
ity graph by using the coefficient of sparse represen-
tation to subspace clustering, called Sparse Subspace
Clustering(SSC). The algorithm based on sparse rep-
resentation techniques and got the sparse coefficient
by using l
1
-minimization, and clustered data by spec-
tral clustering. The spectral clustering algorithm em-
ployed k-means algorithm for data clustering, how-
ever the k-means algorithm is sensitive to the choice
of initial starting conditions [9, 10] and the process
of the algorithm need iterations. In the literatures,
some modified algorithms are available: Scalable S-
parse Subspace Clustering(SSSC) [11] and Reweight-
ed Sparse Subspace Clustering [12]. Kernel version
[13, 14] can also be gotten. Patel et al. [15] introduces
an algorithm Latent Space Sparse Subspace Cluster-
ing based on SSC.
In this paper, two modified SSC algorithms are
proposed in order to avoid the drawbacks of k-means
which gets uncertain results and needs iterations. We
also improve the efficiency of the algorithm. By ob-
serving the structure of the adjacent matrix, we find
that the nonzero element of columns of matrix is in
the same position as the corresponding eigenvector,
therefore we can get the clusters by comparing nonze-
ro elements in the columns of adjacent matrix and the
eigenvectors. k-means algorithm also can be instead
of by SOM algorithm which can gets better result-
s. We do experiments on synthetic data sets and face
clustering data sets, the results show that our proposed
algorithms are better than original SSC [7, 8].
The rest of paper is organized as follows. We
briefly describe the sparse subspace clustering in sec-
tion 2. In section 3 we analysis SSC algorithm and
propose our algorithms. Experimental evaluation is p-
resented in section 4. Finally section 5 conclude our
work.
International Journal of Mathematical and Computational Methods
http://www.iaras.org/iaras/journals/ijmcm