Round trip conversion for an R matrix to a 'faer' matrix in Rust

round-trip-r-matrix-to-faer-matrix.R

library(rextendr) # Version 0.4.0

rust_code <- r"(
use faer::prelude::*;
use extendr_api::prelude::*;

#[extendr]
fn return_matrix(X: RMatrix<f64>) -> RMatrix<f64> {
  let A: Mat<f64> = Mat::from_fn(X.nrows(), X.ncols(), |row, col| X[[row, col]]);
  let result: RMatrix<f64> = RMatrix::new_matrix(A.nrows(), A.ncols(), |row, col| A[(row, col)]);
  return result;
}
)"

rust_source(
  code = rust_code,
  dependencies = list(`faer` = '0.22.6')
)

X <- diag(3)

return_matrix(X)

#>      [,1] [,2] [,3]
#> [1,]    1    0    0
#> [2,]    0    1    0
#> [3,]    0    0    1