OPLS-DA Score Plot of the Six Collections

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 R² and Q² value, then all blue Q²-values to the left are lower than the original points to the right and the blue regression line of the Q²-points intersects the vertical axis (on the left) below zero, thus strongly indicating that the original model was valid.