General sample design. Left panel: matrix DB, appending 34 datasets. Computation of two D/Sthreshold ratios (see text) determines different zones in the matrix. The light grey zone contains DEGs and is integrated to the subset matrix (right panel) as such. The dark grey zone contains the non DEGs. 19,800 rows are selected randomly within this zone to form the background of the subset matrix. A twilight zone segregates the DEGs from the non DEGs.