The (φ_KL, θ_KL) classification of ≈170,000 SDSS galaxy spectra. The right‐hand bar ("a") illustrates the sequence along which the galaxy spectral types are identified. The left‐hand bar ("b") indicates outliers, mostly spectra without significant spectral features. The angles are in degrees. Most outliers have large errors in their redshift estimations, while 90% have low S/N. The boxes are areas in which the mean of all of the observed spectra correspond to red, blue, and emission‐line galaxies. See Fig. 9 for the mean spectra.