A Progressive Combined Variable Selection Method for Near-Infrared Spectral Analysis Based on Three-Step Hybrid Strategy

Table 5

Prediction results of organic matter content in soil by different variable selection methods.

Variable selection methods	Number of variables	nLV	Rc^2	RMSEC (%)	Rp^2	RMSEP (%)
None	1,050	10	0.976	184.25	0.749	318.79
CARS	72	8	0.985 ± 0.002	146.77 ± 10.15	0.916 ± 0.022	154.80 ± 22.36
VCPA	8	7	0.978 ± 0.016	151.41 ± 10.53	0.948 ± 0.031	122.40 ± 20.24
IRIV	11	9	0.983 ± 0.006	149.90 ± 12.13	0.933 ± 0.027	139.06 ± 15.47
SiPLS	140	8	0.985 ± 0.007	143.04 ± 15.89	0.876 ± 0.035	240.06 ± 24.19
IVSO	202	8	0.982 ± 0.009	152.96 ± 16.43	0.923 ± 0.029	148.41 ± 24.18
BOSS	50	10	0.987 ± 0.003	134.07 ± 24.73	0.901 ± 0.024	168.21 ± 25.12
IVSO-BOSS	26	6	0.985 ± 0.003	145.44 ± 21.31	0.891 ± 0.187	193.45 ± 22.74
SiPLS-IVSO	68	8	0.987 ± 0.001	137.22 ± 10.74	0.977 ± 0.168	95.41 ± 12.54
SiPLS-BOSS	13	7	0.988 ± 0.001	131.71 ± 11.85	0.971 ± 0.013	108.80 ± 20.57
CARS-IVSO-BOSS	6	8	0.901 ± 0.027	200.57 ± 20.64	0.682 ± 0.058	347.23 ± 24.13
SiPLS-VCPA-BOSS	9	6	0.984 ± 0.017	142.87 ± 13.54	0.941 ± 0.067	204.19 ± 27.10
SiPLS-IVSO-IRIV	15	8	0.983 ± 0.002	131.71 ± 12.64	0.977 ± 0.029	100.04 ± 16.47
SiPLS-IVSO-BOSS	10	9	0.988 ± 0.001	129.99 ± 10.07	0.979 ± 0.009	94.03 ± 11.76