Discussion of “multivariate functional outlier detection” by M. Hubert, P. Rousseeuw and P. Segaert

This paper aims at discussing the interesting paper of Hubert et al. (2015), where a taxonomy of functional outliers and both numerical and graphical techniques for outlier detection for multivariate functional data are proposed. The reading has been really pleasant and instructive. We contribute to the discussion of the paper by Hubert et al. (2015), by discussing some points related to the extension of depth measures to the multivariate functional framework, by examining the fine line between outlier detection and classification and finally by pointing out some relevant open problems.