QR downdate after removing one row

Updates a QR factorization to reflect the removal of a single row from the original matrix. The current implementation refits from the reduced matrix; a Givens-rotation path is planned for a future release.

Usage

qr_downdate(qr_factor, row_idx, X = NULL)

Arguments

qr_factor

An amQR factor object returned by am_qr(), or any object for which a method is defined.

row_idx

Positive integer index of the row to remove.

X

The original numeric matrix or adgeMatrix used to compute qr_factor. Required for amQR factors because they do not store the source matrix.

Value

An updated amQR factor with row row_idx excluded.

See also

am_qr, qr_info, lm_loo_cv

Examples

if (FALSE) { # \dontrun{
X <- adgeMatrix(matrix(rnorm(40), nrow = 8))
qf <- am_qr(X)
qf2 <- qr_downdate(qf, row_idx = 3L, X = X)
qr_info(qf2)$dim
} # }