Table 2.

The process of variable selection

Feature group	Total features	Preselected features a	Selected features within feature group b	Features finally selected c
Moment-based features	76	71	8	1
Form-based features	86	74	16	4
Statistical features	130	86	46	29
Structural features	108	90	23	10
Spectral features	70	21	6	2
Total	470	342	99	46

Numbers of features are shown. ^aPreselection due to high correlations between features. ^bFeature group scores were constructed with these features. ^cThe final score was constructed with these features.