http://en.wikipedia.org/wiki/Eigenface http://en.wikipedia.org/wiki/Eigenface comes to mind also http://en.wikipedia.org/wiki/Singular_value_decomposition http

http://en.wikipedia.org/wiki/Eigenface http://en.wikipedia.org/wiki/Eigenface comes to mind also http://en.wikipedia.org/wiki/Singular_value_decomposition http://en.wikipedia.org/wiki/Singular_value_decomposition seems to pop up every couple of months or so in a "Oh they do that with SVD?" way