Compute the Inverse Vectorization (AIRM) — airm

Converts a vector back into a tangent matrix relative to a reference point using AIRM.

airm_unvec(sigma, w)

Arguments

sigma: A symmetric positive-definite matrix of class dppMatrix, representing the reference point.
w: A numeric vector, representing the vectorized tangent image.

Value

A symmetric matrix of class dspMatrix, representing the tangent vector.

Examples

if (requireNamespace("Matrix", quietly = TRUE)) {
  library(Matrix)
  sigma <- diag(2) |>
    Matrix::nearPD() |>
    _$mat |>
    Matrix::pack()
  w <- c(1, sqrt(2), 2)
  airm_unvec(sigma, w)
}
#> 2 x 2 Matrix of class "dspMatrix"
#>      [,1] [,2]
#> [1,]    1    1
#> [2,]    1    2