Figure 2.

(a) Principal component analysis score plot and (b) the corresponding partial least square analysis discriminant analysis (PLS-DA) cross-validated score plot generated from the gas chromatography–time-of-flight–mass spectrometry spectra of fecal samples from healthy controls (HCs) (♦) and Crohn's disease (CD) patients in remission (Harvey-Bradshaw index (HBI)≤4, Δ) and not in remission (HBI>4, ○), and cross-validated prediction from the PLS-DA model for (c) HCs vs. CD patients and (d) CD patients in remission vs. not in remission. In (c–d), the predicted group has a target value of y=1, the other two groups have target value y=0, and the discriminant threshold (y∼0.5) is the dashed line.