Fig. 4From: No effect of 25-hydroxyvitamin D supplementation on the skeletal muscle transcriptome in vitamin D deficient frail older adultsMultilevel principle component analysis (PCA) of gene expression data could not distinguish the four experimental groups. Sample plot from an unsupervised multilevel PCA. In multilevel PCA the paired structure of the data, i.e. measurements performed before and after intervention on the same subject, is taken into account to eliminate the inherent between-subject variation. Results revealed no separation between the experimental groupsBack to article page