RSpectra-compatible symmetric eigen shim.

Mirrors RSpectra::eigs_sym(): only the lower (or upper) triangle of a dense or Matrix input is read, values are returned in decreasing order, and sigma requests the eigenvalues nearest the shift.

Usage

eigs_sym(
  A,
  k,
  which = "LM",
  sigma = NULL,
  opts = list(),
  lower = TRUE,
  ...,
  n = NULL,
  args = NULL
)

Arguments

A: Matrix, eigencore operator, or a function f(x, args) returning A %*% x (then n is required).
k: Number of eigenpairs to compute.
which: RSpectra-style target selector ("LM", "SM", "LA", "SA", "BE").
sigma: Optional shift; eigenvalues nearest sigma are returned.
opts: RSpectra options list. tol, ncv (Krylov subspace size, passed as auto(max_subspace = ncv), or lanczos(max_subspace = ncv) when initvec forces a Lanczos route), maxitr (passed as the iteration limit maxit), retvec and initvec are honoured; other keys raise a warning.
lower: Whether to read the lower (TRUE) or upper (FALSE) triangle of a matrix input.
...: Additional arguments passed to eig_partial().
n: Dimension of the operator when A is a function.
args: Extra argument passed to a function A.

Value

A list compatible with RSpectra::eigs_sym(), including values, vectors, convergence counts, operation counts, certificate diagnostics, and eigencore diagnostics.

Examples

A <- diag(c(5, 4, 3, 2, 1))
res <- eigs_sym(A, k = 2, which = "LA")
res$values
#> [1] 5 4