**Figure 2:** ** OPLS-DA Score Plot of the Six Collections over 520 Days.** a,
data from different period were marked by varied symbol styles and color
codes: 1^{st} period (red circle), 2^{nd} period (blue box), 3^{rd} period (turquoise
triangle), 4^{th} period (purple inverted triangle), 5^{th} period (blue diamond),
and 6^{th} period (black pentagon); b, Permutations plot for O2PLS-DA Model
with 200 iterations. The green and blue line each represents regression
line of R^{2} and Q^{2} value, then all blue Q^{2}-values to the left are lower than
the original points to the right and the blue regression line of the Q^{2}-points
intersects the vertical axis (on the left) below zero, thus strongly indicating
that the original model was valid. |