Ranking and significance of variable-length similarity-based time series motifs

The detection of very similar patterns in a time series, commonly called motifs, has received continuous and increasing attention from diverse scientific communities. In particular, recent approaches for discovering similar motifs of different lengths have been proposed. In this work, we show that such variable-length similarity-based motifs cannot be directly compared, and hence ranked, by their normalized dissimilarities. Specifically, we find that length-normalized motif dissimilarities still have intrinsic dependencies on the motif length, and that lowest dissimilarities are particularly affected by this dependency. Moreover, we find that such dependencies are generally non-linear and change with the considered data set and dissimilarity measure. Based on these findings, we propose a solution to rank those motifs and measure their significance. This solution relies on a compact but accurate model of the dissimilarity space, using a beta distribution with three parameters that depend on the motif length in a non-linear way. We believe the incomparability of variable-length dissimilarities could go beyond the field of time series, and that similar modeling strategies as the one used here could be of help in a more broad context.Comment: 20 pages, 10 figure

An empirical evaluation of similarity measures for time series classification

Time series are ubiquitous, and a measure to assess their similarity is a core part of many computational systems. In particular, the similarity measure is the most essential ingredient of time series clustering and classification systems. Because of this importance, countless approaches to estimate time series similarity have been proposed. However, there is a lack of comparative studies using empirical, rigorous, quantitative, and large-scale assessment strategies. In this article, we provide an extensive evaluation of similarity measures for time series classification following the aforementioned principles. We consider 7 different measures coming from alternative measure 'families', and 45 publicly-available time series data sets coming from a wide variety of scientific domains. We focus on out-of-sample classification accuracy, but in-sample accuracies and parameter choices are also discussed. Our work is based on rigorous evaluation methodologies and includes the use of powerful statistical significance tests to derive meaningful conclusions. The obtained results show the equivalence, in terms of accuracy, of a number of measures, but with one single candidate outperforming the rest. Such findings, together with the followed methodology, invite researchers on the field to adopt a more consistent evaluation criteria and a more informed decision regarding the baseline measures to which new developments should be compared. © 2014 Elsevier B.V. All rights reserved.We thank the people who made available or contributed to the UCR time series repository. This research has been funded by 2009-SGR-1434 from Generalitat de Catalunya, JAEDOC069/2010 from Consejo Superior de Investigaciones Científicas, and TIN2009-13692-C03-01 and TIN2012-38450-C03-03 from the Spanish Government, and EU Feder funds. Funding DetailsPeer Reviewe

Association between sella turcica bridging and altered direction of dental eruption : a case-control study

Calcification between the anterior and posterior clinoid processes, also the so-called sella turcica bridging, has been associated in some studies with skeletal anomalies as well as with dental and eruption disturbances. It was hypothesized that sella turcica bridging was associated with an altered direction of dental eruption. The aim of the study was to assess whether there was a relationship between the degree of calcification and the presence or absence of an alteration in the tooth eruption direction. A case-control multicenter study was conducted. The study population consisted of 150 subjects (age 10-50 years), 30 of which presented some type of alteration of the direction canine eruption (impactation or transposition) (cases) and 120 selected at random who did not present altered direction of dental eruption (controls). Cases and controls were matched by age, sex, and approximate date of starting orthodontic treatment. Lateral cephalometric radiographies were obtained and the extent of the sella turcica bridging was measured using a Vernier caliper and scored as no calcification, partially calcified, and completely calcified. The frequency of a partially or completely calcified sella turcica bridge was significantly higher among cases with altered direction of dental eruption as compared with controls. There was a trend towards a shorter length of sella turcica in subjects with two or more canine eruption alterations. Sella turcica bridging was unrelated to sex, but it was significantly influenced by age. Sella turcica bridging is frequently detected in subjects with altered direction of dental eruption of canines

Playing with Cases: Rendering Expressive Music with Case-Based Reasoning

This article surveys long-term research on the problem of rendering expressive music by means of AI techniques with an emphasis on case-based reasoning (CBR). Following a brief overview discussing why people prefer listening to expressive music instead of nonexpressive synthesized music, we examine a representative selection of well-known approaches to expressive computer,music performance with an emphasis on AI-related approaches. In the main part of the article we focus on the existing CBR approaches to the problem of synthesizing expressive music, and particularly on Tempo-Express, a case-based reasoning system developed at our Institute, for applying musically acceptable tempo transformations to monophonic audio recordings of musical performances. Finally we briefly describe an ongoing extension of our previous work consisting of complementing audio information with information about the gestures of the musician. Music is played through our bodies, therefore capturing the gesture of the performer is a fundamental aspect that has to be taken into account in future expressive music renderings. This article is based on the >2011 Robert S. Engelmore Memorial Lecture> given by the first author at AAAI/IAAI 2011.This research is partially supported by the Ministry of Science and Innovation of Spain under the project NEXT-CBR (TIN2009-13692-C03-01) and the Generalitat de Catalunya AGAUR Grant 2009-SGR-1434Peer Reviewe

Estimation of Guitar Fingering and Plucking Controls based on Multimodal Analysis of Motion, Audio and Musical Score

This work presents a method for the extraction of instrumental controls during guitar performances. The method is based on the analysis of multimodal data consisting of a combination of motion capture, audio analysis and musical score. High speed video cameras based on marker identification are used to track the position of finger bones and articulations and audio is recorded with a transducer measuring vibration on the guitar body. The extracted parameters are divided into left hand controls, i.e. fingering (which string and fret is pressed with a left hand finger) and right hand controls, i.e. the plucked string, the plucking finger and the characteristics of the pluck (position, velocity and angles with respect to the string). Controls are estimated based on probability functions of low level features, namely, the plucking instants (i.e. note onsets), the pitch and the distances of the fingers (both hands) to strings and frets. Note onsets are detected via audio analysis, the pitch is extracted from the score and distances are computed from 3D Euclidean Geometry. Results show that by combination of multimodal information, it is possible to estimate such a comprehensive set of control features, with special high performance for the fingering and plucked string estimation. Regarding the plucking finger and the pluck characteristics, their accuracy gets lower but improvements are foreseen including a hand model and the use of high-speed cameras for calibration and evaluation.A. Perez-Carrillo was supported by a Beatriu de Pinos grant 2010 BP-A 00209 by the Catalan Research Agency (AGAUR) and J. Ll. Arcos was supported by ICT -2011-8-318770 and 2009-SGR-1434 projectsPeer reviewe

Cognitive prognosis of acquired brain injury patients using machine learning techniques

The cognitive prognosis of acquired brain injury (ABI) patients is a valuable tool for an improved and personalized treatment. In this paper, we explore the task of automatic cognitive prognosis of ABI patients via machine learning techniques. Based on a set of pre-treatment assessments, distinct classifiers are trained to predict whether the patient will improve in one or any of three cognitive areas: attention, memory, and executive functioning. Results show that variables such as the age at the moment of the injury, the patient's etiology, or the neuropsychological evaluation scores obtained before the treatment are relevant for prognosis and easily yield statistically significant accuracies. Additionally, the prognostic relevance of these and other variables is studied by means of standard feature selection methodologies. The outputs of the present paper add to the discussion on current cognitive rehabilitation practices and push towards the exploitation of existing technologies for improving medical evaluations and treatments.We thank all the patients and staff from Institut Guttmann who cooperated in data collection. This work has been partially funded by TIN-2012-38450-C03-03 from the Spanish Government (all authors), JAEDOC069/2010 from Consejo Superior de Investigaciones Cientıficas (J.S.), and 2009-SGR-1434 from Generalitat de CatalunyaPeer Reviewe

Measuring quantitative trends in western popular music

Popular music is a key cultural expression that has captured listeners' attention for ages. Many of the structural regularities underlying musical discourse are yet to be discovered and, accordingly, their historical evolution remains formally unknown. We find a number of patterns and metrics characterizing the generic usage of primary musical facets such as pitch, timbre, and loudness in contemporary western popular music. Many of these patterns and metrics have been consistently stable for a period of more than fifty years. However, we prove important changes or trends related to the restriction of pitch transitions, the homogenization of the timbral palette, and the growing loudness levels. This suggests that our perception of the new would be rooted on these changing characteristics. Hence, an old tune could perfectly sound novel and fashionable, provided that it consisted of common harmonic progressions, changed the instrumentation, and increased the average loudness.Peer Reviewe