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Oriol Ramos Terrades; Albert Berenguel; Debora Gil |
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A flexible outlier detector based on a topology given by graph communities |
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2020 |
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Arxiv |
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Outlier, or anomaly, detection is essential for optimal performance of machine learning methods and statistical predictive models. It is not just a technical step in a data cleaning process but a key topic in many fields such as fraudulent document detection, in medical applications and assisted diagnosis systems or detecting security threats. In contrast to population-based methods, neighborhood based local approaches are simple flexible methods that have the potential to perform well in small sample size unbalanced problems. However, a main concern of local approaches is the impact that the computation of each sample neighborhood has on the method performance. Most approaches use a distance in the feature space to define a single neighborhood that requires careful selection of several parameters. This work presents a local approach based on a local measure of the heterogeneity of sample labels in the feature space considered as a topological manifold. Topology is computed using the communities of a weighted graph codifying mutual nearest neighbors in the feature space. This way, we provide with a set of multiple neighborhoods able to describe the structure of complex spaces without parameter fine tuning. The extensive experiments on real-world data sets show that our approach overall outperforms, both, local and global strategies in multi and single view settings. |
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IAM; DAG; 600.139; 600.145; 600.140; 600.121 |
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Admin @ si @ RBG2020 |
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3475 |
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Author |
Oriol Ramos Terrades; Albert Berenguel; Debora Gil |
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Title |
A Flexible Outlier Detector Based on a Topology Given by Graph Communities |
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Journal Article |
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Year |
2022 |
Publication |
Big Data Research |
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BDR |
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29 |
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100332 |
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Classification algorithms; Detection algorithms; Description of feature space local structure; Graph communities; Machine learning algorithms; Outlier detectors |
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Outlier detection is essential for optimal performance of machine learning methods and statistical predictive models. Their detection is especially determinant in small sample size unbalanced problems, since in such settings outliers become highly influential and significantly bias models. This particular experimental settings are usual in medical applications, like diagnosis of rare pathologies, outcome of experimental personalized treatments or pandemic emergencies. In contrast to population-based methods, neighborhood based local approaches compute an outlier score from the neighbors of each sample, are simple flexible methods that have the potential to perform well in small sample size unbalanced problems. A main concern of local approaches is the impact that the computation of each sample neighborhood has on the method performance. Most approaches use a distance in the feature space to define a single neighborhood that requires careful selection of several parameters, like the number of neighbors.
This work presents a local approach based on a local measure of the heterogeneity of sample labels in the feature space considered as a topological manifold. Topology is computed using the communities of a weighted graph codifying mutual nearest neighbors in the feature space. This way, we provide with a set of multiple neighborhoods able to describe the structure of complex spaces without parameter fine tuning. The extensive experiments on real-world and synthetic data sets show that our approach outperforms, both, local and global strategies in multi and single view settings. |
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August 28, 2022 |
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DAG; IAM; 600.140; 600.121; 600.139; 600.145; 600.159 |
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Admin @ si @ RBG2022a |
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3718 |
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Antonio Clavelli; Dimosthenis Karatzas; Josep Llados |
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A framework for the assessment of text extraction algorithms on complex colour images |
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Conference Article |
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2010 |
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9th IAPR International Workshop on Document Analysis Systems |
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19–26 |
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The availability of open, ground-truthed datasets and clear performance metrics is a crucial factor in the development of an application domain. The domain of colour text image analysis (real scenes, Web and spam images, scanned colour documents) has traditionally suffered from a lack of a comprehensive performance evaluation framework. Such a framework is extremely difficult to specify, and corresponding pixel-level accurate information tedious to define. In this paper we discuss the challenges and technical issues associated with developing such a framework. Then, we describe a complete framework for the evaluation of text extraction methods at multiple levels, provide a detailed ground-truth specification and present a case study on how this framework can be used in a real-life situation. |
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Boston; USA; |
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978-1-60558-773-8 |
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DAS |
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DAG |
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DAG @ dag @ CKL2010 |
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1432 |
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Author |
Muhammad Muzzamil Luqman; Josep Llados; Jean-Yves Ramel; Thierry Brouard |
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Title |
A Fuzzy-Interval Based Approach For Explicit Graph Embedding, Recognizing Patterns in Signals, Speech, Images and Video |
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Conference Article |
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2010 |
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20th International Conference on Pattern Recognition |
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6388 |
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93–98 |
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We present a new method for explicit graph embedding. Our algorithm extracts a feature vector for an undirected attributed graph. The proposed feature vector encodes details about the number of nodes, number of edges, node degrees, the attributes of nodes and the attributes of edges in the graph. The first two features are for the number of nodes and the number of edges. These are followed by w features for node degrees, m features for k node attributes and n features for l edge attributes — which represent the distribution of node degrees, node attribute values and edge attribute values, and are obtained by defining (in an unsupervised fashion), fuzzy-intervals over the list of node degrees, node attributes and edge attributes. Experimental results are provided for sample data of ICPR2010 contest GEPR. |
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Springer, Heidelberg |
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0302-9743 |
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978-3-642-17710-1 |
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ICPR |
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DAG |
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DAG @ dag @ LLR2010 |
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1459 |
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Author |
Ernest Valveny; Philippe Dosch |
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Title |
A general framework for the evaluation of symbol recognition methods |
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2006 |
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International Journal on Document Analysis and Recognition |
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DAG @ dag @ VaD2006 |
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686 |
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Ernest Valveny; Philippe Dosch; Adam Winstanley; Yu Zhou; Su Yang; Luo Yan; Liu Wenyin; Dave Elliman; Mathieu Nicolas Delalandre; Eric Trupin; Sebastien Adam; Jean-Marc Ogier |
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A general framework for the evaluation of symbol recognition methods |
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2006 |
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International Journal on Document Analysis and Recognition (IJDAR), 9(1): 59–74 |
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DAG @ dag @ VDW2006 |
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801 |
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Author |
Ernest Valveny; Philippe Dosch |
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Title |
A General Framework for the Evaluation of Symbol Recognition Methods |
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2007 |
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International Journal on Document Analysis and Recognition, vol. 9(1), pp 59–74 |
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DAG @ dag @ VaD2007 |
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893 |
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Josep Llados; Dimosthenis Karatzas; Joan Mas; Gemma Sanchez |
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A Generic Architecture for the Conversion of Document Collections into Semantically Annotated Digital Archives |
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2008 |
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Journal of Universal Computer Science |
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14 |
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18 |
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2912–2935 |
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Median Graph, Graph Embedding, Graph Matching, Structural Pattern Recognition |
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DAG @ dag @ LKM2008 |
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1142 |
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Author |
Miquel Ferrer; Dimosthenis Karatzas; Ernest Valveny; I. Bardaji; Horst Bunke |
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Title |
A Generic Framework for Median Graph Computation based on a Recursive Embedding Approach |
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2011 |
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Computer Vision and Image Understanding |
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CVIU |
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115 |
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7 |
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919-928 |
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Median Graph, Graph Embedding, Graph Matching, Structural Pattern Recognition |
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The median graph has been shown to be a good choice to obtain a represen- tative of a set of graphs. However, its computation is a complex problem. Recently, graph embedding into vector spaces has been proposed to obtain approximations of the median graph. The problem with such an approach is how to go from a point in the vector space back to a graph in the graph space. The main contribution of this paper is the generalization of this previ- ous method, proposing a generic recursive procedure that permits to recover the graph corresponding to a point in the vector space, introducing only the amount of approximation inherent to the use of graph matching algorithms. In order to evaluate the proposed method, we compare it with the set me- dian and with the other state-of-the-art embedding-based methods for the median graph computation. The experiments are carried out using four dif- ferent databases (one semi-artificial and three containing real-world data). Results show that with the proposed approach we can obtain better medi- ans, in terms of the sum of distances to the training graphs, than with the previous existing methods. |
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IAM @ iam @ FKV2011 |
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1831 |
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Author |
Adria Molina; Lluis Gomez; Oriol Ramos Terrades; Josep Llados |
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Title |
A Generic Image Retrieval Method for Date Estimation of Historical Document Collections |
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Conference Article |
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2022 |
Publication |
Document Analysis Systems.15th IAPR International Workshop, (DAS2022) |
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13237 |
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583–597 |
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Date estimation; Document retrieval; Image retrieval; Ranking loss; Smooth-nDCG |
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Date estimation of historical document images is a challenging problem, with several contributions in the literature that lack of the ability to generalize from one dataset to others. This paper presents a robust date estimation system based in a retrieval approach that generalizes well in front of heterogeneous collections. We use a ranking loss function named smooth-nDCG to train a Convolutional Neural Network that learns an ordination of documents for each problem. One of the main usages of the presented approach is as a tool for historical contextual retrieval. It means that scholars could perform comparative analysis of historical images from big datasets in terms of the period where they were produced. We provide experimental evaluation on different types of documents from real datasets of manuscript and newspaper images. |
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La Rochelle, France; May 22–25, 2022 |
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DAS |
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DAG; 600.140; 600.121 |
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Admin @ si @ MGR2022 |
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3694 |
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