MSc Defence: Pi-Weighted Sparse Group Lasso for Variable Selection in Finite Mixture Regression Models (Vinay Joshy)

CANDIDATE: Vinay Joshy

ABSTRACT: 

When analyzing heterogeneous data with latent subpopulations, finite mixture regression (FMR) models are effective as they allow for variations in regression coefficients across mixture components. Variable selection is important at two levels: (1) at the group level by removing completely irrelevant covariates across all subpopulations and (2) at the individual level by removing irrelevant covariates within each subpopulation. However, existing variable selection methods for FMR focus solely on individual-level regression coefficient selection, providing no mechanism for group-level variable elimination. We introduce a component-weighted sparse group LASSO regularization method that performs efficient variable selection at both levels simultaneously in finite mixture regression models belonging to the exponential family. We develop a novel optimization procedure through a Majorization-Minimization algorithm. Simulation studies under Gaussian and Poisson mixture regression settings demonstrate reliable recovery of the true sparsity structure at both levels.The method is illustrated by analyzing two real datasets.