Table 5.
Subspace | Preprocessing | R2 for calibration set; n = 1329 |
Q2 for validation set; n = 575 |
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pH | m3.Al | m3.Ca | C | Clay | Sand | pH | m3.Al | m3.Ca | C | Clay | Sand | ||
HQI | First derivative | 0.86 | 0.88 | 0.91 | 0.93 | 0.78 | 0.77 | 0.60 | 0.82 | 0.59 | 0.86 | 0.80 | 0.83 |
Second derivative | 0.90 | 0.90 | 0.91 | 0.92 | 0.80 | 0.79 | 0.73 | 0.79 | 0.65 | 0.85 | 0.78 | 0.84 | |
Msc | 0.81 | 0.82 | 0.89 | 0.90 | 0.74 | 0.70 | 0.10 | 0.50 | 0.10 | 0.10 | 0.63 | 0.60 | |
SNV | 0.80 | 0.96 | 0.98 | 0.98 | 0.93 | 0.83 | 0.33 | 0.69 | 0.10 | 0.75 | 0.81 | 0.82 | |
SNV_Detrend | 0.80 | 0.82 | 0.89 | 0.92 | 0.74 | 0.72 | 0.35 | 0.73 | 0.10 | 0.77 | 0.78 | 0.81 | |
Cosine | First derivative | 0.83 | 0.85 | 0.90 | 0.88 | 0.74 | 0.73 | 0.61 | 0.84 | 0.50 | 0.85 | 0.75 | 0.78 |
Second derivative | 0.85 | 0.86 | 0.89 | 0.89 | 0.78 | 0.77 | 0.69 | 0.83 | 0.62 | 0.79 | 0.75 | 0.78 | |
Msc | 0.79 | 0.81 | 0.89 | 0.89 | 0.73 | 0.72 | 0.10 | 0.10 | 0.10 | 0.10 | 0.43 | 0.34 | |
SNV | 0.78 | 0.80 | 0.88 | 0.87 | 0.73 | 0.72 | 0.55 | 0.76 | 0.10 | 0.63 | 0.73 | 0.73 | |
SNV_Detrend | 0.79 | 0.82 | 0.88 | 0.91 | 0.74 | 0.72 | 0.44 | 0.72 | 0.22 | 0.78 | 0.73 | 0.74 | |
SOM | First derivative | 0.85 | 0.88 | 0.91 | 0.92 | 0.79 | 0.78 | 0.59 | 0.78 | 0.41 | 0.86 | 0.79 | 0.80 |
Second derivative | 0.89 | 0.90 | 0.91 | 0.92 | 0.80 | 0.80 | 0.71 | 0.81 | 0.54 | 0.84 | 0.79 | 0.82 | |
Msc | 0.80 | 0.81 | 0.90 | 0.91 | 0.74 | 0.72 | 0.10 | 0.06 | 0.10 | 0.40 | 0.46 | 0.61 | |
SNV | 0.81 | 0.81 | 0.89 | 0.92 | 0.74 | 0.71 | 0.53 | 0.77 | 0.55 | 0.81 | 0.76 | 0.76 | |
SNV_Detrend | 0.80 | 0.81 | 0.89 | 0.93 | 0.74 | 0.71 | 0.46 | 0.77 | 0.57 | 0.80 | 0.75 | 0.77 | |
Archetype | First derivative | 0.87 | 0.89 | 0.91 | 0.93 | 0.79 | 0.78 | 0.60 | 0.79 | 0.41 | 0.87 | 0.79 | 0.80 |
Second derivative | – | – | – | – | – | – | – | – | – | – | – | – | |
Msc | 0.80 | 0.82 | 0.89 | 0.91 | 0.75 | 0.72 | 0.10 | 0.06 | 0.10 | 0.40 | 0.47 | 0.61 | |
SNV | 0.81 | 0.83 | 0.89 | 0.90 | 0.74 | 0.71 | 0.53 | 0.79 | 0.55 | 0.79 | 0.76 | 0.76 | |
SNV_Detrend | 0.80 | 0.82 | 0.88 | 0.93 | 0.76 | 0.73 | 0.46 | 0.78 | 0.56 | 0.80 | 0.77 | 0.79 | |
All | First derivative | 0.87 | 0.89 | 0.91 | 0.93 | 0.79 | 0.78 | 0.62 | 0.84 | 0.29 | 0.78 | 0.79 | 0.81 |
Second derivative | 0.74 | 0.85 | 0.67 | 0.86 | 0.80 | 0.81 | 0.52 | 0.80 | 0.21 | 0.72 | 0.80 | 0.84 | |
Msc | 0.82 | 0.83 | 0.90 | 0.92 | 0.75 | 0.72 | 0.10 | 0.17 | 0.10 | 0.26 | 0.45 | 0.39 | |
SNV | 0.82 | 0.83 | 0.89 | 0.92 | 0.75 | 0.72 | 0.58 | 0.78 | 0.28 | 0.77 | 0.75 | 0.75 | |
SNV_Detrend | 0.81 | 0.84 | 0.89 | 0.93 | 0.75 | 0.73 | 0.49 | 0.78 | 0.29 | 0.80 | 0.76 | 0.76 |