Computes thin SVD and returns right singular vectors (principal components in the time dimension).
.svd_csa(Z, npc = NULL, criterion = c("er", "gr"))A list with V_k (T x k matrix of PCs), eigenvalues, and k.
Numeric matrix (T x K) of CSA variables.
Integer: number of principal components to retain. If NULL,
determined by ER/GR criterion.
Character: "er" (eigenvalue ratio) or "gr" (growth
ratio). Default "er".