A high-throughput quantification of resin and rubber contents in Parthenium argentatum using near-infrared (NIR) spectroscopy

Table 4 Comparisons of eight different pretreatment approaches in the prediction of adjusted rubber

Cross validation	DRY + IRR					DRY					IRR
Cross validation	\({\text{R}}_{\text{CV}}^{2}\)	RMSECV	RMSEC	RMSECV/RMSEC	F	\({\text{R}}_{\text{CV}}^{2}\)	RMSECV	RMSEC	RMSECV/RMSEC	F	\({\text{R}}_{\text{CV}}^{2}\)	RMSECV	RMSEC	RMSECV/RMSEC	F
No preprocessing	0.652	0.899	0.885	1.016	7	0.661	0.898	0.868	1.035	7	0.632	0.794	0.776	1.022	7
Smoothing	0.653	0.897	0.885	1.013	7	0.665	0.892	0.868	1.028	7	0.629	0.796	0.777	1.026	7
Smoothing + normalization	0.642	0.912	0.900	1.013	7	0.682	0.870	0.853	1.021	7	0.614	0.813	0.794	1.023	7
Smoothing + baseline + normalization	0.658	0.890	0.883	1.008	7	0.658	0.900	0.868	1.037	7	0.625	0.801	0.781	1.025	7
SNV	0.660	0.890	0.878	1.013	7	0.684	0.866	0.846	1.024	7	0.631	0.794	0.776	1.023	7
SNV + DT	0.667	0.879	0.870	1.011	7	0.699	0.846	0.818	1.034	7	0.641	0.784	0.766	1.023	7
SNV + DT + 1st derivative	0.683	0.857	0.846	1.014	5	0.718	0.819	0.776	1.056	7	0.667	0.755	0.740	1.020	4
SNV + DT + 2nd derivative	0.733	0.788	0.731	1.078	7	0.756	0.763	0.661	1.153	7	0.728	0.683	0.599	1.140	7

External validation	\({\text{R}}_{\text{P}}^{2}\)	RMSEP	RMSEC	RMSEP/RMSEC	F	RPD	\({\text{R}}_{\text{P}}^{2}\)	RMSEP	RMSEC	RMSEP/RMSEC	F	RPD	\({\text{R}}_{\text{P}}^{2}\)	RMSEP	RMSEC	RMSEP/RMSEC	F	RPD
SNV + DT + 2nd derivative	0.756	0.753	0.731	1.030	7	2.024	0.780	0.724	0.661	1.095	7	2.128	0.755	0.647	0.618	1.047	6	2.019

Smoothing: median filter smoothing; Normalization: normalization by mean; Baseline: offset and linear baseline correction; SNV: standard normal variate; DT: de-trending, 2nd polynomial; Savitzky–Golay 1st derivative, 2nd polynomial, 23 smoothing points; Savitzky–Golay 2nd derivative, 2nd polynomial, 23 smoothing points
R², coefficient of determination; RMSECV, root mean squared error of cross validation; RMSEC, root mean squared error of calibration; CV, cross validation; EV, external validation; F, number of factors (latent values) used in calibration; RPD, ratio of performance over prediction)

ISSN: 1746-4811