PCA_UPDATE - Principal Component Analysis of a rank-l 
  updated matrix with MATLAB (eigs)
    [U, S, V]=PCA_UPDATE(A, W, H, C, K) computes the K-factor 
    Principal Component Analysis of A - W * H, i.e. SVD of 
    (A - W * H) - C * ones(size(A, 2), 1), using the svds 
    function of MATLAB.
 
  Copyright 2011 Dimitrios Zeimpekis, Eugenia Maria Kontopoulou, 
                 Efstratios Gallopoulos