Performance of the best spectroscopic models as measured against the test set.

aSpectral transformation (SG0 =  Savitzky-Golay smoothing; SG1 =  Savitzky-Golay first derivative; SNV = standard normal variate);
bMultivariate Calibration Model (svm = support vector machine regression; cubist = Cubist);
cPredictor used in the models (spc = spectral matrix; rfe = spectral matrix with bands selected by recursive feature elimination);
dStandard Deviation of the observations (g C kg−1);
eRoot Mean Square Error of Prediction (g C kg−1; Eq. 4);
fBias (g C kg−1; Eq. 2);
gStandard Error of Prediction (g C kg−1; Eq. 3);
hRatio of Performance to Deviation (Eq. 5);
iNumber of validation samples.