How Many Dissimilarity/Kernel Self Organizing Map Variants Do We Need?

In numerous applicative contexts, data are too rich and too complex to be represented by numerical vectors. A general approach to extend machine learning and data mining techniques to such data is to really on a dissimilarity or on a kernel that measures how different or similar two objects are. This approach has been used to define several variants of the Self Organizing Map (SOM). This paper reviews those variants in using a common set of notations in order to outline differences and similarities between them. It discusses the advantages and drawbacks of the variants, as well as the actual relevance of the dissimilarity/kernel SOM for practical applications

Vektorių kvantavimo metodų ir daugiamačių skalių junginys daugiamačiams duomenims vizualizuoti

Darbe pateikiama lyginamoji dviejų vektorių kvantavimo metodų (saviorganizuojančių neuroninių tinklų ir neuroninių dujų) analizė. Neuronai nugalėtojai, kurie gaunami vektorių kvantavimo metodais, yra vizualizuojami daugiamačių skalių metodu. Tirta kvantavimo paklaidos priklausomybė nuo vektorių nugalėtojų skaičiaus. Išsiaiškinta, kuris vektorių kvantavimo metodas yra tinkamesnis jungti su daugiamačių skalių metodu, t. y. vizualizavus neuronus nugalėtojus „atskleidžiama“ analizuojamųduomenų struktūra.Combination of Vector Quantization and Multidimensional ScalingAlma Molytė, Olga Kurasova SummaryIn this paper, we present a comparative analysis of a combination of two vector quantization methods (self-organizing map (SOM) and neural gas (NG)), based on neural networks and multidimensional scaling that is used for visualization of codebook vectors obtained by vector quantization methods. The dependence of neuron-winners, quantization and mapping qualities, and preserving of a data structure in the mapping image are investigated. It is established that the quantization errors of NG are smaller than that of the SOM when the number of neurons-winners is approximately equal. It means that the neural gas is more suitable for vector quantization. The data structure is visible in the mapping image even when the number r of neurons-winners of NG is small enough. If the number r of neurons-winners of the SOM is larger, the data structure is visible, as well.8px;">&nbsp

Web-Based Visualization of Very Large Scientific Astronomy Imagery

Visualizing and navigating through large astronomy images from a remote location with current astronomy display tools can be a frustrating experience in terms of speed and ergonomics, especially on mobile devices. In this paper, we present a high performance, versatile and robust client-server system for remote visualization and analysis of extremely large scientific images. Applications of this work include survey image quality control, interactive data query and exploration, citizen science, as well as public outreach. The proposed software is entirely open source and is designed to be generic and applicable to a variety of datasets. It provides access to floating point data at terabyte scales, with the ability to precisely adjust image settings in real-time. The proposed clients are light-weight, platform-independent web applications built on standard HTML5 web technologies and compatible with both touch and mouse-based devices. We put the system to the test and assess the performance of the system and show that a single server can comfortably handle more than a hundred simultaneous users accessing full precision 32 bit astronomy data.Comment: Published in Astronomy & Computing. IIPImage server available from http://iipimage.sourceforge.net . Visiomatic code and demos available from http://www.visiomatic.org