Data clustering is an important and frequently used unsupervised learning method. Recent research has demonstrated that incorporating instance-level background information to traditional clustering algorithms can increase the clustering performance. In this paper, we extend traditional clustering by introducing additional prior knowledge such as the size of each cluster. We propose a heuristic algorithm to transform size constrained clustering problems into integer linear programming problems. Experiments on both synthetic and UCI datasets demonstrate that our proposed approach can utilize cluster size constraints and lead to the improvement of clustering accuracy.

Data clustering with size constraints

Document clustering is automatic organization of documents into clusters so that documents within a cluster have high similarity in comparison to documents in other clusters. It has been studied intensively because of its wide applicability in various areas such as web mining, search engines, and information retrieval. It is measuring similarity between documents and grouping similar documents together. It provides efficient representation and visualization of the documents; thus helps in easy navigation also. In this paper, we have given overview of various document clustering methods studied and researched since last few years, starting from basic traditional methods to fuzzy based, genetic, coclustering, heuristic oriented etc. Also, the document clustering procedure with feature selection process, applications, challenges in document clustering, similarity measures and evaluation of document clustering algorithm is explained.

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Document Clustering: A Detailed Review

This paper addresses the problem of semantics-based temporal expert finding, which means identifying a person with given expertise for different time periods. For example, many real world applications like reviewer matching for papers and finding hot topics in newswire articles need to consider time dynamics. Intuitively there will be different reviewers and reporters for different topics during different time periods. Traditional approaches used graph-based link structure by using keywords based matching and ignored semantic information, while topic modeling considered semantics-based information without conferences influence (richer text semantics and relationships between authors) and time information simultaneously. Consequently they result in not finding appropriate experts for different time periods. We propose a novel Temporal-Expert-Topic (TET) approach based on Semantics and Temporal Information based Expert Search (STMS) for temporal expert finding, which simultaneously models conferences influence and time information. Consequently, topics (semantically related probabilistic clusters of words) occurrence and correlations change over time, while the meaning of a particular topic almost remains unchanged. By using Bayes Theorem we can obtain topically related experts for different time periods and show how experts' interests and relationships change over time. Experimental results on scientific literature dataset show that the proposed generalized time topic modeling approach significantly outperformed the non-generalized time topic modeling approaches, due to simultaneously capturing conferences influence with time information.

https://iiu.edu.pk/wp-content/uploads/downloads/faculties/fbas/cs/ali_daud/Ali_RP/2010-KBS%20Journal-Temporal%20expert%20finding%20through%20generalized%20time%20topic%20modeling.pdf

Temporal expert finding through generalized time topic modeling

The discovery, extraction and analysis of knowledge from data rely generally upon the use of unsupervised learning methods, in particular clustering approaches. Much recent research in clustering and data engineering has focused on the consideration of finite mixture models which allow to reason in the face of uncertainty and to learn by example. The adoption of these models becomes a challenging task in the presence of outliers and in the case of high-dimensional data which necessitates the deployment of feature selection techniques. In this paper we tackle simultaneously the problems of cluster validation (i.e. model selection), feature selection and outliers rejection when clustering positive data. The proposed statistical framework is based on the generalized inverted Dirichlet distribution that offers a more practical and flexible alternative to the inverted Dirichlet which has a very restrictive covariance structure. The learning of the parameters of the resulting model is based on the minimization of a message length objective incorporating prior knowledge. We use synthetic data and real data generated from challenging applications, namely visual scenes and objects clustering, to demonstrate the feasibility and advantages of the proposed method.

Robust simultaneous positive data clustering and unsupervised feature selection using generalized inverted Dirichlet mixture models

Text documents usually contain high dimensional non-discriminative (irrelevant and noisy) terms which lead to steep computational costs and poor learning performance of text classification. One of the effective solutions for this problem is feature selection which aims to identify discriminative terms from text data. This paper proposes a method termed “Hebb rule based feature selection (HRFS)”. HRFS is based on supervised Hebb rule and assumes that terms and classes are neurons and select terms under the assumption that a term is discriminative if it keeps “exciting” the corresponding classes. This assumption can be explained as “a term is highly correlated with a class if it is able to keep “exciting” the class according to the original Hebb postulate. Six benchmarking datasets are used to compare HRFS with other seven feature selection methods. Experimental results indicate that HRFS is effective to achieve better performance than the compared methods. HRFS can identify discriminative terms in the view of synapse between neurons. Moreover, HRFS is also efficient because it can be described in the view of matrix operation to decrease complexity of feature selection.

Supervised Hebb rule based feature selection for text classification

The task of selecting relevant features is a hard problem in the field of unsupervised text clustering due to the absence of class labels that would guide the search. This paper proposes a new mixture model method for unsupervised text clustering, named multinomial mixture model with feature selection (M3FS). In M3FS, we introduce the concept of component-dependent ''feature saliency'' to the mixture model. We say a feature is relevant to a certain mixture component if the feature saliency value is higher than a predefined threshold. Thus the feature selection process is treated as a parameter estimation problem. The Expectation-Maximization (EM) algorithm is then used for estimating the model. The experiment results on commonly used text datasets show that the M3FS method has good clustering performance and feature selection capability.

Liang Zhang

Papers

Multinomial mixture model with feature selection for text clustering