“…In the case of S-shaped and V-shaped conversion functions, the number of each dimension feature data belonging to the optimal feature subset is counted, as shown in Figure 7. It can be seen from Figure 7 that the number of the 3rd, 13th, 22nd, 23rd, 24th, and 31st dimensions of the optimal feature subsets is the largest, but the final optimal feature subsets {1, 3,10,11,12,13,14,18,19,21,23,24,29,30,31} do not incorporate all of these higherfrequency features (that is, the optimal feature subset is not a simple combination of features with high frequency). The optimal feature subset does not necessarily include features with high frequency, since the feature subset selected by features of high frequency only may not have the best classification effect.…”