Figure 4.

Quality of the principal component models was evaluated with the parameters R² and Q². R² is the explained variance, Q² is the predictive ability of the model validation, and correlation is the degree of overlap between the permuted and original models. The validation model exhibited good predictive ability, as indicated by the high Q² value. Grey triangles, the goodness of fit was quantified by R²; black squares, the predictive ability was indicated by Q² (R²Y=0.802, Q²Y=0.643).