Le lundi 03 novembre 2014 à 15:00 - UM2 - Bât 09 - Salle de conférence (1er étage)Julien Stoehr
Selecting between different dependency structures of hidden Markov random field can be very challenging, due to the intractable normalizing constant in the likelihood. We answer this question with approximate Bayesian computation (ABC) which provides a model choice method in the Bayesian paradigm. This comes after the work of Grelaud, et al. (2009) who exhibited sufficient statistics on directly observed Gibbs random fields. But when random field is latent, the sufficiency falls and we complement the set with geometric summary statistics. The general approach to construct these intuitive statistics relies on a clustering analysis of the sites based on the observed colors and plausible latent graphs. The efficiency of ABC model choice based on these statistics is evaluated via a local error rate which may be of independent interest. As a byproduct we derived an ABC algorithm that adapts the dimension of the summary statistics to the dataset without distorting the model selection. Mots clés : Approximate Bayesian computation, Model choice, Hidden Gibbs random fields, Summary statistics, Misclassification rate, k -nearest neighbors Référence : J. Stoehr, P. Pudlo, L. Cucala, Adaptive ABC model choice and geometric summary statistics for hidden Gibbs random fields, Statistics and Computing, 2014.