Table 3.
Quantitative relationship between SOM and spectral variables of different numbers of dimensions in the calibration (n = 112) and validation (n = 56) datasets.
| Dimensions | Spectral Variables | Linear Model | R 2 c | RMSEc (g kg−1) | R 2 v | RMSEv (g kg−1) | RPIQ |
|---|---|---|---|---|---|---|---|
| 1DV | PC1 | y = 24.79 − 0.88x | 0.14 | 16.44 | 0.01 | 16.36 | 0.67 |
| PC2 | y = 8.59 + 3.22x | 0.10 | 11.30 | 0.07 | 12.20 | 0.82 | |
| PC3 | y = 8.40 − 1.17x | 0.01 | 11.82 | 0.18 | 12.77 | 0.81 | |
| PC4 | y = 4.18 + 13.72x | 0.19 | 10.97 | 0.09 | 13.79 | 0.87 | |
| PC5 | y = 7.79 − 11.90x | 0.04 | 11.21 | 0.01 | 15.00 | 0.86 | |
| 2DI | SI (R2260, R1450) | y = 27.85 − 25.56x | 0.34 | 11.79 | 0.34 | 12.59 | 1.08 |
| DI (R800, R790) | y = 20.03 − 348.35x | 0.46 | 9.19 | 0.43 | 9.98 | 1.03 | |
| PI (R1490, R2340) | y = 21.08 − 86.87x | 0.33 | 9.13 | 0.30 | 10.92 | 1.04 | |
| RI (R785, R805) | y = −70.94 + 83.80x | 0.47 | 9.58 | 0.49 | 10.38 | 1.10 | |
| NDI (R800, R790) | y = 19.38 − 353.96x | 0.48 | 9.19 | 0.46 | 9.98 | 1.03 | |
| 3DI | TBI1 (R2265, R2230, R1465) | y = −83.16 + 174.51x | 0.69 | 6.95 | 0.64 | 7.65 | 1.34 |
| TBI2 (R2215, R1460, R2255) | y = 128.19 − 62.75x | 0.71 | 6.14 | 0.70 | 6.86 | 1.50 | |
| TBI3 (R1890, R2065, R2265) | y = −4.32 − 21.12x | 0.72 | 7.79 | 0.68 | 8.54 | 1.23 | |
| TBI4 (R1895, R2095, R2295) | y = 2.21 − 8.06x | 0.70 | 8.19 | 0.68 | 8.53 | 1.23 | |
| TBI5 (R2200, R1455, R2280) | y = 9.28 − 263.26x | 0.65 | 7.22 | 0.64 | 8.00 | 1.29 |