Applies accelerated proximal gradient algorithm to the l1-regularized quadratic program $$f(\mathbf{x}) + g(\mathbf{x}) = \frac{1}{2}\mathbf{x}^TA\mathbf{x} - d^T\mathbf{x} + \lambda |\mathbf{x}|_1$$
APG_EN2(A, d, x0, lam, alpha, maxits, tol)p by p positive definite coefficient matrix $$A = (\gamma Om + X^T X/n)$$.
nx1 dimensional column vector.
Regularization parameter for l1 penalty, must be greater than zero.
Step length.
Number of iterations to run
Stopping tolerance for proximal gradient algorithm.
APG_EN2 returns an object of class "APG_EN2" including a list
with the following named components
callThe matched call.
xFound solution.
kNumber of iterations used.
This function is used by other functions and should only be called explicitly for debugging purposes.
Used by: SDAAP and the SDAAPcv cross-validation version.