Two semi-supervised locality sensitive k-means clustering algorithms by seeding

Semi-supervised clustering takes advantage of some labeled data called seeds to bring a great benefit to the clustering of unlabeled data. This paper presents a novel semi-supervised clustering method based on one-class support vector machine, which applies a novel decision rule to assigning the class label to one data point. To investigate the effectiveness of our approach, experiments are done on one artificial data set and two real datasets. Experimental results show that the proposed method can improve the clustering performance significantly compared to other semi-supervised clustering algorithms when using a very small amount of seeds.

During the past few years, semi-supervised clustering has emerged as a new interesting direction in machine learning research. In a semi-supervised clustering algorithm, the clustering results can be significantly improved by using side information, which is available or collected from users. There are two main kinds of side information that can be learned in semi-supervised clustering algorithms: the class labels - called seeds or the pairwise constraints. The first semi-supervised clustering was introduced in 2000, and since that, many algorithms have been presented in literature. However, it is not easy to use both types of side information in the same algorithm. To address the problem, this paper proposes a semi-supervised graph based clustering algorithm that tries to use seeds and constraints in the clustering process, called MCSSGC. Moreover, we introduces a simple but efficient active learning method to collect the constraints that can boost the performance of MCSSGC, named KMMFFQS. In order to verify effectiveness of the proposed algorithm, we conducted a series of experiments not only on real data sets from UCI, but also on a document data set applied in an Information Extraction of Vietnamese documents. These obtained results show that the proposed algorithm can significantly improve the clustering process compared to some recent algorithms.

Currently, breast cancer is one of the most common cancers among women. To aid clinicians in diagnosis, lesion regions in mammography pictures can be segmented using an artificial intelligence system. This has significant clinical implications. Clustering algorithms, as unsupervised models, are widely used in medical image segmentation. However, due to the different sizes and shapes of lesions in mammography images and the low contrast between lesion areas and the surrounding pixels, it is difficult to use traditional unsupervised clustering methods for image segmentation. In this study, we try to apply the semisupervised fuzzy clustering algorithm to lesion segmentation in mammography molybdenum target images and propose semisupervised fuzzy clustering based on the cluster centres of labelled samples (called SFCM_V, where V stands for cluster centre). The algorithm refers to the cluster centre of the labelled sample dataset during the clustering process and uses the information of the labelled samples to guide the unlabelled samples during clustering to improve the clustering performance. We compare the SFCM_V algorithm with the current popular semisupervised clustering algorithm and an unsupervised clustering algorithm and perform experiments on real patient mammogram images using DICE and IoU as evaluation metrics; SFCM_V has the highest evaluation metric coefficient. Experiments demonstrate that SFCM_V has higher segmentation accuracy not only for larger lesion regions, such as tumours, but also for smaller lesion regions, such as calcified spots, compared with existing clustering algorithms.

Clustering aims to partition a data set into homogenous groups which gather similar objects. Object similarity, or more often object dissimilarity, is usually expressed in terms of some distance function. This approach, however, is not viable when dissimilarity is conceptual rather than metric. In this paper, we propose to extract the dissimilarity relation directly from the available data. To this aim, we train a feedforward neural network with some pairs of points with known dissimilarity. Then, we use the dissimilarity measure generated by the network to guide a new unsupervised fuzzy relational clustering algorithm. An artificial data set and a real data set are used to show how the clustering algorithm based on the neural dissimilarity outperforms some widely used (possibly partially supervised) clustering algorithms based on spatial dissimilarity.

This paper presents semi-supervised agglomerative hierarchical clustering algorithm using clusterwise tolerance based pairwise constraints. In semi-supervised clustering, pairwise constraints, that is, must-link and cannot-link, are frequently used in order to improve clustering properties. From that sense, we will propose another way named clusterwise tolerance based pairwise constraints to handle must-link and cannot-link constraints inL2-space. In addition, we will propose semi-supervised agglomerative hierarchical clustering algorithm based on it. We will, moreover, show the effectiveness of the proposed method through numerical examples.

Semi-supervised clustering leverages side information such as pairwise constraints to guide clustering procedures. Despite promising progress, existing semi-supervised clustering approaches overlook the condition of side information being generated sequentially, which is a natural setting arising in numerous real-world applications such as social network and e-commerce system analysis. Given emerged new constraints, classical semi-supervised clustering algorithms need to re-optimize their objectives over all data samples and constraints in availability, which prevents them from efficiently updating the obtained data partitions. To address this challenge, we propose an efficient dynamic semi-supervised clustering framework that casts the clustering problem into a search problem over a feasible convex set, i.e., a convex hull with its extreme points being an ensemble of m data partitions. According to the principle of ensemble clustering, the optimal partition lies in the convex hull, and can thus be uniquely represented by an m-dimensional probability simplex vector. As such, the dynamic semi-supervised clustering problem is simplified to the problem of updating a probability simplex vector subject to the newly received pairwise constraints. We then develop a computationally efficient updating procedure to update the probability simplex vector in O(m2) time, irrespective of the data size n. Our empirical studies on several real-world benchmark datasets show that the proposed algorithm outperforms the state-of-the-art semi-supervised clustering algorithms with visible performance gain and significantly reduced running time.

Development of novel combustion risk index for flammable liquids based on unsupervised clustering algorithms

A novel semi-supervised clustering algorithm is proposed that synergizes the benefits of supervised and unsupervised learning methods. Data are clustered using an unsupervised learning technique biased toward producing clusters as pure as possible in terms of class distribution. These clusters can then be used to predict the class of future points. For example, in database marketing this technique can be used to identify and characterize segments of the customer population likely to respond to a specific promotion. One key additional benefit of this approach is that it allows unlabeled data with unknown class to be used to improve classification accuracy. The objective function of a traditional clustering technique, cluster dispersion in the K-means algorithm, is modified to minimize both the within-cluster variance of the input attributes and a measure of cluster impurity based on the class labels. Minimizing the within-cluster variance of the examples is a form of capacity control to prevent overfitting...

Semi-supervised clustering algorithms introduce partial knowledge into traditional unsupervised methods and generally improve results. Partial constrained clustering is one of the main kinds of semi-supervised clustering algorithms. Notably, constraints selected at random might probable bring only trivial improvement. To improve both the effectiveness and the efficiency of the partial constrained clustering algorithms, active selection for constraints is important. However, there are only few studies on the selection of active constraints. In view of this problem, in this paper we propose an improved selection approach of active constraints for partial constrained clustering algorithms. Compared to the state-of-the-art Explore and Consolidate approach, Experiments on a number of public benchmark data sets show that (i) our approach can find more informational constraints for partial constrained clustering algorithms and bring encouraging improvement; and (ii) our approach can find out constraints distributed among all the classes in investigated data sets quickly, which shows that our approach can be used in more occasions when only small numbers of constraints are allowed.

Semi-supervised clustering is a special form of classification that uses a large amount of unlabeled data together with labeled data to achieve better classification results. This paper introduces a semi-supervised fuzzy clustering algorithm of relational data with multiple prototype representation (SS-CLAMP) that aims to furnish a partition and a set of prototypes for each fuzzy cluster as well as to learn a relevance weight for each dissimilarity matrix by optimizing an adequacy criterion that measures the fit between the fuzzy clusters and their representatives in a competitive way and that takes into account pairwise constraints must-link and cannot-link. Experiments with real-valued data sets show the usefulness of the proposed algorithm.

Semi-supervised clustering has been widely explored in the last years. In this paper, we present HCAC-ML (Hierarchical Confidence-based Active Clustering with Metric Learning), an innovative approach for this task which employs distance metric learning through cluster-level constraints. HCAC-ML is based on the HCAC algorithm, an state-of-the-art algorithm for hierarchical semi-supervised clustering that uses an active learning approach for inserting cluster-level constraints. These constraints are presented to a variation of ITML (Information-theoretic Metric Learning) algorithm to learn a Mahalanobis-like distance function. We compared HCAC-ML with other semi-supervised clustering algorithms in 26 different datasets. Results indicate that HCAC-ML outperforms other algorithms in most of the scenarios, but specially when the number of constraints is small. This makes HCAC-ML useful in practical applications.

Clustering algorithms are popular algorithms used in various fields of science and engineering and technologies. The k-means is example unsupervised clustering algorithm used in various applications such as medical images clustering, gene data clustering etc. There is huge research work done on basic k-means clustering algorithm for its enhancement. But researchers focused only on some of the limitations of k-means. This paper studied some of literatures on improved k-means algorithms, summarized their shortcomings and identified scope for further enhancement to make it more scalable and efficient for large data. From the literatures this paper studied distance, validity and stability measures, algorithms for initial centroids selection and algorithms to decide value of k. Then proposing objectives and guidelines for enhanced scalable clustering algorithm. Also suggesting method to avoid outliers using concept of semantic analysis and AI.

Clustering is often considered as an unsupervised data analysis method, but making full use of the prior information in the process of clustering will significantly improve the performance of the clustering algorithm. Spectral clustering algorithm can well use the prior pairwise constraint information to cluster and has become a new hot spot of machine learning research in recent years. In this paper, we propose an effective clustering algorithm, called a semi-supervised spectral clustering algorithm based on pairwise constraints, in which the similarity matrix of data points is adjusted and optimized by pairwise constraints. The experiments on real-world data sets demonstrate the effectiveness of this algorithm.

Structural heterogeneity in single-particle cryo-electron microscopy (cryo-EM) data represents a major challenge for high-resolution structure determination. Unsupervised classification may serve as the first step in the assessment of structural heterogeneity. However, traditional algorithms for unsupervised classification, such as K-means clustering and maximum likelihood optimization, may classify images into wrong classes with decreasing signal-to-noise-ratio (SNR) in the image data, yet demand increased computational costs. Overcoming these limitations requires further development of clustering algorithms for high-performance cryo-EM data processing. Here we introduce an unsupervised single-particle clustering algorithm derived from a statistical manifold learning framework called generative topographic mapping (GTM). We show that unsupervised GTM clustering improves classification accuracy by about 40% in the absence of input references for data with lower SNRs. Applications to several experimental datasets suggest that our algorithm can detect subtle structural differences among classes via a hierarchical clustering strategy. After code optimization over a high-performance computing (HPC) environment, our software implementation was able to generate thousands of reference-free class averages within hours in a massively parallel fashion, which allows a significant improvement on ab initio 3D reconstruction and assists in the computational purification of homogeneous datasets for high-resolution visualization.

In unsupervised clustering tasks, incorporating pairwise constraints as prior information has become an effective approach to improve clustering quality. Building upon the efficient clustering algorithm k-sums, which unifies the frameworks of K-means and Ratio-cut, this paper introduces a novel semi-supervised clustering algorithm by integrating prior pairwise constraints. On one hand, the proposed method inherits the ability of k-sums to handle large-scale data and complex cluster structures with linear time complexity. On the other hand, it enhances clustering discriminability and robustness through constraint-based optimization under semi-supervised settings. Experimental results on multiple benchmark datasets demonstrate that the proposed method significantly outperforms existing mainstream semi-supervised clustering approaches in both clustering accuracy and computational efficiency, showing strong practical value and promising scalability.