if p ∈ [2, P ], the objective function can be written as: if p = 1, the objective function can be written as: j be the j th column vector of D p , and v (p) j be the j th column vector of V p , respectively.
equation (8) can be rewritten as: (10) which can be decomposed into N optimization problems that can be solved independently, with each corresponding to one column of V p : Equation 12is a least square problem with L 2 norm regularization.