Shrinkage Function And Its Applications In Matrix Approximation
  The shrinkage function is widely used in matrix low-rank approximation, compressive sensing, and statistical estimation. In this article, an elementary derivation of the shrinkage function is given. In addition, applications of the shrinkage function are demonstrated in solving several well-known problems, together with a new result in matrix approximation. 
Toby Boas, Aritra Dutta, Xin Li, Kathryn P. Mercier, Eric Niderman
math.OC