Table 4.

Rotation values for each variable along principal component 1 (PC1). After principal component analysis (PCA) was conducted on the training data set using prcomp function, PC1 was the principal component that showed the clearest separation between infested and noninfested trees and also accounted for the most variability in the training data set based on 3D PCA score plot. Corresponding rotation values of 6 variables along PC1 were obtained to show the correlation between these variables and PC1.