Table 2.

Error evaluations of full-spectrum among different preprocessing methods for metal ions concentration prediction.

	Preprocessing	MAPE(%)	MaxAPE(%)	RMSE${}_{\mathbf{CV}}$(mg/L)	${\mathit{R}}^2$
	Raw	13.777	21.534	4.785	0.792
Zinc	Denoising	16.718	24.621	4.947	0.749
	1st derivative	8.744	13.220	4.242	0.892
	2nd derivative	8.235	11.395	3.941	0.921
	Raw	13.762	18.781	0.145	0.746
Copper	Denoising	8.023	12.789	0.115	0.924
	1st derivative	7.236	11.604	0.105	0.938
	2nd derivative	11.819	14.355	0.139	0.824
	Raw	11.213	23.958	0.131	0.773
Cobalt	Denoising	11.051	21.545	0.146	0.737
	1st derivative	10.792	17.897	0.134	0.756
	2nd derivative	6.254	12.032	0.099	0.901
	Raw	12.463	23.057	0.143	0.779
Nickel	Denoising	8.529	14.573	0.114	0.907
	1st derivative	9.322	15.496	0.118	0.894
	2nd derivative	17.758	25.619	0.150	0.738