K-nearest-neighbors spectral modeling

K-nearest-neighbors is all the rage in Camp Hogg these days. Pursuant to our conversations this week, I wrote a short document explaining how we could use it to determine G-dwarf ages with SEGUE spectra. The issue is that you want to see very subtle chromospheric activity on top of coincident absorption lines. You need a good model of each spectrum, better than theoretical models or spectral libraries can provide. My document explains how you could do it with the large extant data set, capitalizing on the neighbors in spectral space. Rix is about to hand me the spectra.