Figure 3.

Raw spectral data and preprocessing techniques. (a) Spectral curves for all samples; (b) average spectral curve across all samples; (c) preprocessing with the Savitzky−Golay (SG) method; (d) preprocessing with multiplicative scatter correction (MSC); (e) preprocessing with standard normal variate (SNV); (f) preprocessing using the first derivative (1D); (g) combined preprocessing with the first derivative and Savitzky−Golay smoothing (1D + SG); (h) combined preprocessing with the first derivative and multiplicative scatter correction (1D + MSC); (i) combined preprocessing with the first derivative and standard normal variate (1D + SNV).