9,375 research outputs found

    Viewpoints: A high-performance high-dimensional exploratory data analysis tool

    Full text link
    Scientific data sets continue to increase in both size and complexity. In the past, dedicated graphics systems at supercomputing centers were required to visualize large data sets, but as the price of commodity graphics hardware has dropped and its capability has increased, it is now possible, in principle, to view large complex data sets on a single workstation. To do this in practice, an investigator will need software that is written to take advantage of the relevant graphics hardware. The Viewpoints visualization package described herein is an example of such software. Viewpoints is an interactive tool for exploratory visual analysis of large, high-dimensional (multivariate) data. It leverages the capabilities of modern graphics boards (GPUs) to run on a single workstation or laptop. Viewpoints is minimalist: it attempts to do a small set of useful things very well (or at least very quickly) in comparison with similar packages today. Its basic feature set includes linked scatter plots with brushing, dynamic histograms, normalization and outlier detection/removal. Viewpoints was originally designed for astrophysicists, but it has since been used in a variety of fields that range from astronomy, quantum chemistry, fluid dynamics, machine learning, bioinformatics, and finance to information technology server log mining. In this article, we describe the Viewpoints package and show examples of its usage.Comment: 18 pages, 3 figures, PASP in press, this version corresponds more closely to that to be publishe

    NASTRAN interfacing modules within the Integrated Analysis Capability (IAC) Program

    Get PDF
    The IAC program provides the framework required for the development of an extensive multidisciplinary analysis capability. Several NASTRAN related capabilities were developed which can all be expanded in a routine manner to meet in-house unique needs. Plans are to complete the work discussed herein and to provide it to the engineering community through COSMIC. Release is to be after the current IAC Level 2 contract work on the IAC executive system is completed and meshed with the interfacing modules and analysis capabilities under development at the GSFC

    Assortment Variety: Attribute versus Product-Based

    Get PDF
    Retailers need to decide on the content and structure of their product assortments, and thereby on the degree of variety that they offer to their customers.This paper compares measures of assortment variety and relates them to underlying variety components.We conceptualize assortment variety from a product and an attribute perspective, compare extant measures of assortment variety, and examine the appropriateness of these measures in capturing assortment variety as perceived by consumers.Recently, Hoch, Bradlow and Wansink (1999) introduced a general model of assortment variety based on product dissimilarities.The current study takes an alternative approach and proposes variety measures based on attributes, specifically the dispersion across attribute levels and the association between the attributes of the products in an assortment.Attribute dispersion refers to the diversity of attribute levels in an assortment (e.g. the relative proportion of red, green, blue products), while association between attributes refers to systematic links between attributes (e.g. all red products are large).We show that product-based and attribute-based approaches to assortment variety lead to substantially different measures with different effects on consumers' perceptions of variety.A first, synthetic, data set, shows that measures of attribute dispersion, attribute association and assortment size reflect specific components of assortment variety.The product-based measure proposed by Hoch et al. is sensitive to the size of the assortment, while the attribute-based measures respond only to specific changes in the content of an assortment.A second, consumer, data set shows that the attribute-based approach accounts best for consumers' perceptions of variety, and offers diagnostic power to retailers by explicating variety components.Attribute-based measures of variety significantly add to the prediction of consumers' perceptions of variety, over and above the product-based variety measures, while the reverse is not the case.In the final section we discuss how attribute-based measures can be used in assortment management, e.g. when assortments of different size are compared, when the impact of adding or dropping products on assortment variety is to be determined, and when diagnostic information about assortment variety is important.product assortment;variety measurement;variety perception;retailing

    On complexity of optimized crossover for binary representations

    Get PDF
    We consider the computational complexity of producing the best possible offspring in a crossover, given two solutions of the parents. The crossover operators are studied on the class of Boolean linear programming problems, where the Boolean vector of variables is used as the solution representation. By means of efficient reductions of the optimized gene transmitting crossover problems (OGTC) we show the polynomial solvability of the OGTC for the maximum weight set packing problem, the minimum weight set partition problem and for one of the versions of the simple plant location problem. We study a connection between the OGTC for linear Boolean programming problem and the maximum weight independent set problem on 2-colorable hypergraph and prove the NP-hardness of several special cases of the OGTC problem in Boolean linear programming.Comment: Dagstuhl Seminar 06061 "Theory of Evolutionary Algorithms", 200

    The Spanish E-retailing Customers Segmentation

    Get PDF
    This article analyses different factors that influence the purchasing behaviour of online supermarket customers. These factors are related to both the appearance of the website as well as the processes that take place when making the purchase. Based on these analyses, the various groups of consumers with homogenous behaviour are studied. The analysis also allows the quality of the service offered by this kind of establishment to be defined, as well as the main dimensions in which it develops. In the conclusions, factors which should influence the manager of an online supermarket to improve the quality of its service are given.Virtual supermarket; segmentation; Internet; E-commerce; marketing.

    Branch and peg algorithms for the simple plant location problem

    Get PDF
    The simple plant location problem is a well-studied problem in combinatorial optimization. It is one of deciding where to locate a set of plants so that a set of clients can be supplied by them at the minimum cost. This problem of ten appears as a subproblem in other combinatorial problems. Several branch and bound techniques have been developed to solve these problems. In this paper we present a few techniques that enhance the performance of branch and bound algorithms. The new algorithms thus obtained are called branch and peg algorithms, where pegging refers to assigning values to variables outside the branching process. We present exhaustive computational experiments which show that the new algorithms generate less than 60% of the number of subproblems generated by branch and bound algorithms, and in certain cases require less than 10% of the execution times required by branch and bound algorithms.

    BCAS: A Web-enabled and GIS-based Decision Support System for the Diagnosis and Treatment of Breast Cancer

    Get PDF
    For decades, geographical variations in cancer rates have been observed but the precise determinants of such geographic differences in breast cancer development are unclear. Various statistical models have been proposed. Applications of these models, however, require that the data be assembled from a variety of sources, converted into the statistical models’ parameters and delivered effectively to researchers and policy makers. A web-enabled and GIS-based system can be developed to provide the needed functionality. This article overviews the conceptual web-enabled and GIS-based system (BCAS), illustrates the system’s use in diagnosing and treating breast cancer and examines the potential benefits and implications for breast cancer research and practice

    Solving the simple plant location problem using a data correcting approach

    Get PDF
    The Data Correcting Algorithm is a branch and bound algorithm in which thedata of a given problem instance is ‘corrected’ at each branching in such a waythat the new instance will be as close as possible to a polynomially solvableinstance and the result satisfies an acceptable accuracy (the difference betweenoptimal and current solution). In this paper the data correcting algorithm isapplied to determining exact and approximate optimal solutions to the simpleplant location problem. Implementations of the algorithm are based on apseudo-Boolean representation of the goal function of the SPLP and a newreduction rule. We study the efficiency of the data correcting approach usingtwo different bounds, the combinatorial bound and the Erlenkotter bound. Wepresent computational results on several benchmark instances of the simpleplant location problem, which confirm the efficiency of the data-correcting approach.
    corecore