Fig. 2

a PCA score plot: gastric ulcer vs gastric carcinoma patients. b OPLSDA score plot: gastric ulcer vs gastric carcinoma patients (3 components, R2X = 0.535, R2Y = 0.616, and Q2 = 0.423). c PLSDA validation plot intercepts: gastric ulcer vs gastric carcinoma patients R2 = (0.0, 0.167); Q2 = (0.0, − 0.163)