bm_repeat_indexing: Re-indexing matrix for repeated mappers

In inlabru-org/inlabru: Bayesian Latent Gaussian Modelling using INLA and Extensions

Re-indexing matrix for repeated mappers

Description

Helper methods for regular and interleaved state vector indexing, meant for use in bru_mapper_repeat mappers.

Usage

bm_repeat_indexing(n_map, n_rep, interleaved = FALSE)

bm_repeat_indexing_matrix(n_map, n_rep)

Arguments

n_map	The block mapper size
n_rep	The number of times the block is repeated
interleaved	logical; if TRUE, the state vector indexing is interleaved. Default is FALSE, for blockwise indexing.

Value

bm_repeat_indexing: Returns a list with a vector of offsets, offsets, and a vector of relative index values, index; block k indexing is given by offsets[k] + index.

bm_repeat_indexing_matrix: A sparseMatrix object.

Functions

• bm_repeat_indexing(): Construct the offsets and within-block index vectors for a repeated mapper, with or without interleaving.

• bm_repeat_indexing_matrix(): Creates a sparse matrix A such that z <- A %*% x constructs a blockwise version z = c(x1, x2, ..., xn) of an interleaved state vector x = c(x1[1], x2[1], ..., x1[2], x2[2], ...). Each block is of size n_map, and there are n_rep blocks. The reverse operation, taking a blockwise z = c(x1, x2, ..., xn) to an interleaved vector is x <- Matrix::t(A) %*% z.

Examples

(idx <- bm_repeat_indexing(3, 2, FALSE))
(idx <- bm_repeat_indexing(3, 2, TRUE))
(A <- bm_repeat_indexing_matrix(3, 2))
(x_interleaved <- 1:6)
(x_blockwise <- as.vector(A %*% x_interleaved))
(x_recovered <- as.vector(Matrix::t(A) %*% x_blockwise))

inlabru-org/inlabru documentation built on April 5, 2025, 2:08 a.m.