59,524 research outputs found
DisC Diversity: Result Diversification based on Dissimilarity and Coverage
Recently, result diversification has attracted a lot of attention as a means
to improve the quality of results retrieved by user queries. In this paper, we
propose a new, intuitive definition of diversity called DisC diversity. A DisC
diverse subset of a query result contains objects such that each object in the
result is represented by a similar object in the diverse subset and the objects
in the diverse subset are dissimilar to each other. We show that locating a
minimum DisC diverse subset is an NP-hard problem and provide heuristics for
its approximation. We also propose adapting DisC diverse subsets to a different
degree of diversification. We call this operation zooming. We present efficient
implementations of our algorithms based on the M-tree, a spatial index
structure, and experimentally evaluate their performance.Comment: To appear at the 39th International Conference on Very Large Data
Bases (VLDB), August 26-31, 2013, Riva del Garda, Trento, Ital
Analyzing and Visualizing State Sequences in R with TraMineR
This article describes the many capabilities offered by the TraMineR toolbox for categorical sequence data. It focuses more specifically on the analysis and rendering of state sequences. Addressed features include the description of sets of sequences by means of transversal aggregated views, the computation of longitudinal characteristics of individual sequences and the measure of pairwise dissimilarities. Special emphasis is put on the multiple ways of visualizing sequences. The core element of the package is the state se- quence object in which we store the set of sequences together with attributes such as the alphabet, state labels and the color palette. The functions can then easily retrieve this information to ensure presentation homogeneity across all printed and graphical displays. The article also demonstrates how TraMineRâÂÂs outcomes give access to advanced analyses such as clustering and statistical modeling of sequence data.
HASH: the Hong Kong/AAO/Strasbourg H-alpha planetary nebula database
By incorporating our major recent discoveries with re-measured and verified
contents of existing catalogues we provide, for the first time, an accessible,
reliable, on-line SQL database for essential, up-to date information for all
known Galactic PNe. We have attempted to: i) reliably remove PN mimics/false
ID's that have biased previous studies and ii) provide accurate positions,
sizes, morphologies, multi-wavelength imagery and spectroscopy. We also provide
a link to CDS/Vizier for the archival history of each object and other valuable
links to external data. With the HASH interface, users can sift, select,
browse, collate, investigate, download and visualise the entire currently known
Galactic PNe diversity. HASH provides the community with the most complete and
reliable data with which to undertake new science.Comment: 8 pages, 4 figures; accepted to appear in refereed proceedings of the
11th Pacific Rim Conference held in Hong-kong in Dec 201
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