Model

Original spectrum

The first derivative spectrum of reciprocal logarithm

R²

RMSE

RPD

R²

RMSE

RPD

linear model

PCA-PLSR

0.7234

0.0384

1.8972

0.7341

0.0382

1.9095

Non-linear model

PCA-SVM

0.7646

0.0377

1.9344

0.8571

0.0264

2.7624

PCA-BPN

0.7844

0.0354

2.1835

0.8642

0.0261

2.7942

PCA-RF

0.8362

0.0301

2.4229

0.9630

0.0197

3.7019