“…Motivated by the Jiang & Zhang () results, Koenker & Mizera () describe implementations for binomial and Gaussian location mixtures that employ modern interior point methods drastically improving both accuracy and speed over prior EM methods. Gu & Koenker () describe several extensions of this approach to longitudinal models. In our longitudinal Robbins setting, denoting g i = g ( y i 1 ,⋯, y i m ), we can formulate the variational problem as follows: As noted by Laird and elaborated by Lindsay () solutions, , in the space, , of distribution functions are discrete with k ≤ n mass points.…”