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Table 3 Coefficients of determination (R2) and root mean square error (RMSE in mg·dm−2) of the indices developed for phenotyping EW in leaves

From: High-resolution spectral information enables phenotyping of leaf epicuticular wax in wheat

Index Model parameters
a B R2 RMSE 95% CI p-value
Broad indices / RGB and NIR spectral bands
 EWI-1 Blue/Red 0.213 0.04 0.44 1.19 1.037–2.17  < 0.0001
 EWI-2 Blue/NIR 0.07 0.13 0.39 1.18 0.98–1.98  < 0.0001
 EWI-3 (NIR-Red)/Blue − 0.93 − 0.01 0.31 1.19 1.04–1.97  < 0.0001
 EWI-4 (Red2-Blue)/(Red-Blue2) − 0.09 − 0.03 0.32 1.19 1.09–2.55  < 0.0001
Narrow indices / two narrow spectral bands
 EWI-5 676 0.019 0.005 0.45 0.97 0.75–1.21  < 0.0001
 EWI-6 658/712 0.12 0.03 0.52 1.02 0.70–1.36  < 0.0001
 EWI-7 625/706 0.22 0.05 0.50 0.96 0.67–1.28  < 0.0001
 EWI-8 694/625 − 0.006 − 0.002 0.42 1.08 0.96–1.55  < 0.0001
 EWI-9 (670–718) / (670+718) − 0.85 0.03 0.51 1.04 0.61–1.54  < 0.0001
 EWI-10 (691–661) / (691+661)2 4.92 − 1.03 0.48 0.99 0.74–1.27  < 0.0001
 EWI-11 (1/661)—(1/694) 29.13 − 5.73 0.48 1.01 0.71–1.35  < 0.0001
 EWI-12 (622/718)-1 0.62 0.12 0.51 0.99 0.74–1.28  < 0.0001
Narrow indices / three narrow spectral bands
 EWI-13 625 (1/736 – 1/832) 0.008 0.004 0.65 1.01 0.622–1.426  < 0.0001
 EWI-14 (625–736) / 832 0.02 0.007 0.62 0.98 0.65–1.35  < 0.0001
  1. R2 was calculated in the training set by a leaving one out cross validation analysis (LOOCV) and the RMSE was estimated in the validation set. B is the slope of the line and a is the intercept of the dependent variable