Figure 11: Boxplots of evaluation values for different methods; the x-axis tick labels correspond to 1: VMD-FE-HGWOSCA-SVM, 2: VMD-PE-HGWOSCA-SVM, 3: EMD-MAR-GWO-SVM, 4: EMD-MAR-MHGWOSCA-SVM, 5: VMD-MAR-GWO-SVM, 6 VMD-MAR-HGWOSCA-SVM, 7: VMD-MAR-SCA-SVM, and 8: VMD-MAR-MHGWOSCA-SVM.