Left: 2D projection of G2+G3 BAL anomalies (using PCA 1 versus PCA 2 coefficients) as grouped into three types by the secondary k-means clustering as discussed in Sect. 3.3. The reddened and FeLoBALs are placed on the upper region with higher PCA 2 coefficients pertaining to largely amount of reddening in their spectra. Flat BALs, usually with a flat spectrum are placed in the middle left region. Right: 2D projection of reddened anomalies (using PCA 1 versus PCA two coefficients) as grouped into three subtypes by the secondary k-means clustering as discussed in Sect. 3.3. The heavily reddened quasars, characterized by steeply sloped spectra, are positioned in the upper region with higher PCA 2 coefficients. Moderately reddened quasars, exhibiting a flat continuum, occupy the middle region. Quasars with plateau-shaped spectra are located in the lower region of the distribution, with the lowest PCA 2 coefficients, due to their overall negative slope.