Table 4.

Prediction accuracies of the As concentration obtained using laboratory spectra and field spectra based on IRIV.

Algorithm	Spectral Type	Models	Calibration Set			Validation Set
			${\mathit{R}}_{\mathit{c}}^2$	$\mathit{R}\mathit{M}\mathit{S}{\mathit{E}}_{\mathit{c}}$	$\mathit{M}\mathit{A}{\mathit{E}}_{\mathit{c}}$	${\mathit{R}}_{\mathit{p}}^2$	$\mathit{R}\mathit{M}\mathit{S}{\mathit{E}}_{\mathit{p}}$	$\mathit{M}\mathit{A}{\mathit{E}}_{\mathit{p}}$
IRIV	Laboratory spectra	PLSR	0.29	0.94	0.73	0.52	0.67	0.49
		BRR	0.91	0.34	0.26	0.79	0.44	0.36
		RR	0.49	0.80	0.62	0.49	0.69	0.56
		KRR	0.55	0.76	0.59	0.48	0.70	0.56
		SVMR	0.99	0.11	0.10	0.59	0.62	0.49
		XGBoost	0.87	0.40	0.31	0.57	0.63	0.49
		RFR	0.78	0.53	0.39	0.27	0.82	0.69
	Field spectra	PLSR	0.27	1.00	0.75	0.37	0.74	0.62
		BRR	0.16	1.07	0.85	0.20	0.84	0.73
		RR	0.28	1.00	0.75	0.37	0.75	0.63
		KRR	0.29	0.99	0.75	0.42	0.72	0.60
		SVMR	0.75	0.59	0.32	0.23	0.83	0.64
		XGBoost	0.99	0.14	0.10	0.29	0.79	0.69
		RFR	0.83	0.49	0.34	0.49	0.67	0.56