Left: Eigen spectra of the eleven principle components with percentage of variances as well as uncertainties, toward W3 IRS5. Right: Scaled channel-wise column density spectra of the eleven species (HCO⁺, HCN, C₂H, c-C₃H₂, CH, OH, O, C⁺, H₂O⁺, OH⁺, and ArH⁺) as a function of υ_LSR. Black curves represent the observational data, and red dotted curves are the spectra reproduced with only the first three principal components (PC-1, PC-2, and PC-3). For C⁺, H₂O⁺, OH⁺, and ArH⁺, the reproduced spectra indicated by blue dotted curves include one or two more PCs, i.e., PC-4 and PC-5.