Figure 2.

PLS-DA and OPLS-DA analysis of GC-MS metabolite profiles. (A) The PLS-DA score plot showed that the asthma samples and control subjects were scattered into two different regions. The X-axis, t[1], and Y-axis, t[2], indicated the first and second principal components, respectively. (B) A permutation test was performed to validate the PLS-DA model. The R² and Q² intercept values were 0.726 and -0.17, respectively after 200 permutations. (C) The OPLS-DA score plot showed that the asthma samples and control subjects were scattered into two different regions. The X-axis, t[1], and Y-axis, t[2], indicated the first and second principal components, respectively. (D) The OPLS-DA loading plot was constructed to display the relationship between the X-variables and the Y-variables for the first predictive component and the first Y-orthogonal component. The horizontal axis represented the X-loadings p and the Y-loadings q of the predictive component. The vertical axis represented the X-loadings p(o) and the Y-loadings s(o) for the Y-orthogonal component. X-variables situated in the vicinity of the dummy Y-variables have the highest discriminatory power between the classes.