Principal Component Analysis of AGN Spectra
  We discuss spectral principal component analysis (SPCA) and show examples of its application in analyzing AGN spectra in both small and large samples. It can be used to identify peculiar spectra and classify AGN spectra. Its application to correlation studies of AGN spectral properties and spectral measurements for large samples is promising. 
Zhaohui Shang, Beverley J. Wills