Results from PCA. Top: full range of the linear combination of Amplitude₂ and Amplitude₃ determined after applying a θ = 30° rotation following Eq. (3). Over-plotted the mean spectrum (black line) determined from all spectra extending to +45 d and covering the wavelength range of 3950–7000 Å. Blue and red shaded regions correspond to the full range of the first rotated PC (0.87 ⋅ Amplitude₃ − 0.50 ⋅ Amplitude₂) with the blue corresponding negative values and red to positive. Balmer series features are indicated with gray regions as in Fig. 2. Bottom: the corresponding linear combination of Amplitude₂ and Amplitude₃, plotted versus phase. This particular linear combination separates particularly well between +20 d to +40 d the SNe IIb from the SNe Ib and SNe Ic.