archetypes

Roweis and I started working on the problem of finding N galaxy spectra that cover all SDSS galaxy spectra. We have to find all of the pairs ij where the spectrum of galaxy i is a good model for the spectrum of galaxy j and then Roweis has an algorithm that finds the smallest subset of the covering spectra i such that every spectrum j in the sample is covered. This subset is a discrete sampling of the entire space of galaxy spectra, or you can think of it as a non-parametric description of that space; we will also identify outliers.