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

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

Cross validationDRY + IRRDRYIRR
\({\text{R}}_{\text{CV}}^{2}\)RMSECVRMSECRMSECV/RMSECF \({\text{R}}_{\text{CV}}^{2}\)RMSECVRMSECRMSECV/RMSECF \({\text{R}}_{\text{CV}}^{2}\)RMSECVRMSECRMSECV/RMSECF 
No preprocessing0.6520.8990.8851.0167 0.6610.8980.8681.0357 0.6320.7940.7761.0227 
Smoothing0.6530.8970.8851.0137 0.6650.8920.8681.0287 0.6290.7960.7771.0267 
Smoothing + normalization0.6420.9120.9001.0137 0.6820.8700.8531.0217 0.6140.8130.7941.0237 
Smoothing + baseline + normalization0.6580.8900.8831.0087 0.6580.9000.8681.0377 0.6250.8010.7811.0257 
SNV0.6600.8900.8781.0137 0.6840.8660.8461.0247 0.6310.7940.7761.0237 
SNV + DT0.6670.8790.8701.0117 0.6990.8460.8181.0347 0.6410.7840.7661.0237 
SNV + DT + 1st derivative0.6830.8570.8461.0145 0.7180.8190.7761.0567 0.6670.7550.7401.0204 
SNV + DT + 2nd derivative0.7330.7880.7311.0787 0.7560.7630.6611.1537 0.7280.6830.5991.1407 
External validation\({\text{R}}_{\text{P}}^{2}\)RMSEPRMSECRMSEP/RMSECFRPD\({\text{R}}_{\text{P}}^{2}\)RMSEPRMSECRMSEP/RMSECFRPD\({\text{R}}_{\text{P}}^{2}\)RMSEPRMSECRMSEP/RMSECFRPD
SNV + DT + 2nd derivative0.7560.7530.7311.03072.0240.7800.7240.6611.09572.1280.7550.6470.6181.04762.019
  1. 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
  2. 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)