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Nombre de programmes trouvés : 76
Conférences

le (39m34s)

Klopp - Sparse Network Estimation

Inhomogeneous random graph models encompass many network models such as stochastic block models and latent position models. We consider the problem of the statistical estimation of the matrix of connection probabilities based on the observations of the adjacency matrix of the network. We will also discuss the problem of graphon estimation when the probability matrix is sampled according to the graphon model. For these two problems, the minimax optimal rates of convergence in Frobenius norm are achieved by the least squares estimator which is known to be NP-hard. In this talk we will present two alternatives to the least squares: ...
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Conférences

le (42m3s)

Verzelen - Clustering with the relaxed K-means

This talk is devoted to clustering problems. It amounts to partitionning a set of given points or the nodes of a given graph, in such a way that the groups are as homogeneous as possible. After introducing two random instances of this problem, namely sub-Gaussian Mixture Model (sGMM) and Stochastic Block Model (SBM), I will explain how convex relaxations of the classical $K$-means criterion achieve near optimal performances. Emphasis will be put on the connections between the clustering bounds and relevant results in random matrix theory.
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Conférences

le (54m25s)

Carpentier - Introduction to some problems of composite and minimax hypothesis testing

A fundamental question in statistics is: how well can we fulfil a given aim given the data that one possesses? Answering this question sheds light on the possibilities, but also on the fundamental limitations, of statistical methods and algorithms. In this talk, we will consider some examples of this question and its answers in the hypothesis testing setting. We will consider the Gaussian model in (high) dimension p where the data are of the form X = \theta + \sigma \epsilon, where \epsilon is a standard Gaussian vector with identity covariance matrix.  An important hypothesis testing question consists in deciding whether \theta belongs to ...
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