Characteristic wavelength model data^a.

Pretreatment method		LVs	Calibration set		Prediction set
			R c	RMSEC	R p	RMSEP	RPD
SNV	CARS	6	0.9186	1.87	0.9258	1.81	2.66
	SPA	6	0.8803	2.25	0.9229	1.82	2.64
MSC	CARS	9	0.9276	1.76	0.9467	1.63	2.95
	SPA	10	0.8905	2.17	0.9272	1.82	2.64
SG	CARS	8	0.9076	1.98	0.9242	1.81	2.66
	SPA	10	0.8857	2.21	0.892	2.17	2.22
SG-SNV	CARS	7	0.9250	1.79	0.9259	1.80	2.67
	SPA	5	0.8807	2.24	0.8546	2.49	1.93
SG-MSC	CARS	7	0.9020	2.06	0.9069	2.06	2.33
	SPA	6	0.8637	2.4	0.8970	2.18	2.21

^a N: number of spectral variables; LVs: number of latent variables; R_c: correlation coefficient in calibration; RMSEC: root mean square errors in calibration; R_p: correlation coefficient in prediction; RMSEP: root mean square errors in prediction; RPD: residual predictive deviation in prediction set.