Analyse des données

Résumé

L’analyse des données (aussi appelée analyse exploratoire des données ou AED) est une famille de méthodes statistiques dont les principales caractéristiques sont d'être multidimensionnelles et descriptives. Dans l'acception française, la terminologie « analyse des données » désigne donc un sous-ensemble de ce qui est appelé plus généralement la statistique multivariée. Certaines méthodes, pour la plupart géométriques, aident à faire ressortir les relations pouvant exister entre les différentes données et à en tirer une information statistique qui permet de décrire de façon plus succincte les principales informations contenues dans ces données. D'autres techniques permettent de regrouper les données de façon à faire apparaître clairement ce qui les rend homogènes, et ainsi mieux les connaître. L’analyse des données permet de traiter un nombre très important de données et de dégager les aspects les plus intéressants de la structure de celles-ci. Le succès de cette discipline dans les

Source officielle

https://fr.wikipedia.org/wiki/Analyse_des_donn%C3%A9es

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées (100)

Publications associées

Chargement

Personnes associées (78)

Personnes associées

Chargement

Unités associées (60)

Afficher plus

Unités associées

Chargement

Concepts associés (50)

Concepts associés

Chargement

Cours associés (199)

Cours associés

Chargement

Séances de cours associées (634)

Séances de cours associées

Chargement

Robust inference for generalized linear models

Sahar Hosseinian Ehrensberger

Generalized Linear Models have become a commonly used tool of data analysis. Such models are used to fit regressions for univariate responses with normal, gamma, binomial or Poisson distribution. Maximum likelihood is generally applied as fitting method. In the usual regression setting the least absolute-deviations estimator (L1-norm) is a popular alternative to least squares (L2-norm) because of its simplicity and its robustness properties. In the first part of this thesis we examine the question of how much of these robustness features carry over to the setting of generalized linear models. We study a robust procedure based on the minimum absolute deviation estimator of Morgenthaler (1992), the Lq quasi-likelihood when q = 1. In particular, we investigate the influence function of these estimates and we compare their sensitivity to that of the maximum likelihood estimate. Furthermore we particularly explore the Lq quasi-likelihood estimates in binary regression. These estimates are difficult to compute. We derive a simpler estimator, which has a similar form as the Lq quasi-likelihood estimate. The resulting estimating equation consists in a simple modification of the familiar maximum likelihood equation with the weights wq(μ). This presents an improvement compared to other robust estimates discussed in the literature that typically have weights, which depend on the couple (xi, yi) rather than on μi = h(xiT β) alone. Finally, we generalize this estimator to Poisson regression. The resulting estimating equation is a weighted maximum likelihood with weights that depend on μ only.

EPFL2009

Chargement

Data cleaning has become an indispensable part of data analysis due to the increasing amount of dirty data. Data scientists spend most of their time preparing dirty data before it can be used for data analysis. Existing solutions that attempt to automate the data cleaning procedure treat data cleaning as a separate offline process that takes place before analysis begins, while also focusing on a specific use-case. In addition, when the analysis involves complex non-relational data such as graphs, data cleaning becomes more challenging as it involves expensive operations. Therefore, offline, specialized cleaning tools exhibit long running times or fail to process large datasets. At the same time, applying data cleaning before analysis starts assumes a priori knowledge of the inconsistencies and the query workload, thereby requiring effort on understanding and cleaning data that is unnecessary for the analysis. Therefore, from a user's perspective, one is forced to use a different, potentially inefficient tool for each category of errors.In this thesis we aim for coverage and efficiency of data cleaning. We design and build data cleaning systems that employ high-level abstractions to (a) represent and optimize different cleaning operations for data of various formats, and (b) allow for real-time data cleaning that is relevant to data analysis.We introduce CleanM, a language that can express multiple types of cleaning operations. CleanM goes through a three-level translation process for optimization purposes; a different family of optimizations is applied in each abstraction level. Thus, CleanM can express complex data cleaning tasks, optimize them in a unified way, and deploy them in a scaleout fashion.To further reduce the data-to-insight time, we propose an approach that performs probabilistic repair of denial constraint violations on-demand, driven by the exploratory analysis that users perform. We introduce Daisy, a system that seamlessly integrates data cleaning into the analysis by relaxing query results. Daisy executes analytical query-workloads over dirty data by weaving cleaning operators into the query plan.To cover complex data such as graphs, we optimize the building block of data cleaning operations on graph data, that is subgraph matching. Subgraph matching constitutes the main bottleneck when cleaning graph data as it is an NP-complete problem. To optimize subgraph matching, we present a scale-up, radix-based algorithm that starts from an arbitrary partitioning of the graph and coordinates parallel pattern matching to eliminate redundant work among the workers. To address load imbalance, we employ a work stealing technique, specific to the subgraph matching problem. Worker threads steal work from straggler threads by using a heuristic that maximizes the work stolen, while at the same time preserves the order of evaluating candidate vertices.Overall, instead of using offline, specialised tools, this thesis designs abstractions that optimize different cleaning primitives over heterogeneous data, while also integrating data cleaning tasks seamlessly into data analysis. Specifically, we provide (a) a declarative high-level interface backed by an optimizable query calculus and (b) the required optimizations at the underlying data cleaning layers while also taking into consideration the exploratory analysis that users perform.

EPFL2021

Chargement

CleanM: An Optimizable Query Language for Unified Scale-Out Data Cleaning

Anastasia Ailamaki, Benjamin Cyrille Damien Gaidioz, Styliani Asimina Giannakopoulou, Manolis Karpathiotakis

Assoc Computing Machinery2017

Chargement

EPFL2021