Table 1.

Percentage of explained variance for the front three PCS

Spectral type	Explained variance (%)
	Training dataset				Testing dataset
	PC1	PC2	PC3	Total	PC1	PC2	PC3	Total
Raw	85.7	13.3	0.8	99.8	78.5	19.9	1.3	99.7
FDR	94.2	4.0	1.0	99.2	75.7	20.9	3.0	99.6
SDR	71.8	9.8	3.9	85.5	87.3	6.3	1.3	94.9