“…Consequently, such characteristics raise challenges and opportunities on dimension reduction and feature selection of longitudinal genomic data. In supervised learning scenarios, time‐course structures of gene expression data have been used for predicting patient outcomes (Zhang et al, ; Zhang and Ouyang, ) and classifying patients (Zhang et al, ). In unsupervised learning scenarios, classical dimension‐reduction techniques, such as principal component analysis (PCA) and sparse PCA (d'Aspremont et al, ), have been widely used in static gene expression data analysis (Ringnér, ), combinational gene regulation modeling (Ouyang et al, ), and genome‐wide association studies (Aschard et al, ).…”