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Clustering by compression
 IEEE Transactions on Information Theory
, 2005
"... Abstract—We present a new method for clustering based on compression. The method does not use subjectspecific features or background knowledge, and works as follows: First, we determine a parameterfree, universal, similarity distance, the normalized compression distance or NCD, computed from the l ..."
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Cited by 197 (23 self)
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Abstract—We present a new method for clustering based on compression. The method does not use subjectspecific features or background knowledge, and works as follows: First, we determine a parameterfree, universal, similarity distance, the normalized compression distance or NCD, computed from the lengths of compressed data files (singly and in pairwise concatenation). Second, we apply a hierarchical clustering method. The NCD is not restricted to a specific application area, and works across application area boundaries. A theoretical precursor, the normalized information distance, codeveloped by one of the authors, is provably optimal. However, the optimality comes at the price of using the noncomputable notion of Kolmogorovcomplexity. We propose axioms to capture the realworld setting, and show that the NCD approximates optimality. To extract a hierarchy of clusters from the distance matrix, we determine a dendrogram (ternary tree) by a new quartet method and a fast heuristic to implement it. The method is implemented and available as public software, and is robust under choice of different compressors. To substantiate our claims of universality and robustness, we report evidence of successful application in areas as diverse as genomics, virology, languages, literature, music, handwritten digits, astronomy, and combinations of objects from completely different domains, using statistical, dictionary, and block sorting compressors. In genomics, we presented new evidence for major questions in Mammalian evolution, based on wholemitochondrial genomic analysis: the Eutherian orders and the Marsupionta hypothesis against the Theria hypothesis. Index Terms—Heterogenous data analysis, hierarchical unsupervised clustering, Kolmogorovcomplexity, normalized compression distance, parameterfree data mining, quartet tree method, universal dissimilarity distance. I.
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, 2007
"... Timing analysis of the MAGIC telescope data after the installation of the ultrafast 2 GSamples/s FADC readout Treball de recerca de Tercer Cicle ..."
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Timing analysis of the MAGIC telescope data after the installation of the ultrafast 2 GSamples/s FADC readout Treball de recerca de Tercer Cicle
P oS(MQW6)021 The Radius Dilemma: A brief look at the QPO FrequencyInner Disk Radius Connection in
"... We examine the evolution of the color radius and GRS 1915+105 and compare that to predictions made by the Magnetic Flood Model. This model applies a linear correction to associate the Low Frequency QPO to the Keplerian frequency. Because spectral fits to the Xray data using XSpec often produce erro ..."
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We examine the evolution of the color radius and GRS 1915+105 and compare that to predictions made by the Magnetic Flood Model. This model applies a linear correction to associate the Low Frequency QPO to the Keplerian frequency. Because spectral fits to the Xray data using XSpec often produce erroneously low color radius results, the quantity is often ignored, but the trend is assumed to be a valid trace of the inner disk radius. We show that, if the radius trend established by the Xray spectral fits can be believed, then no monotonic solution can rectify the QPO frequency to the Keplerian radius. We discuss various caveats and analases that may be performed to further test the Magnetic Flood model.