RcppArmadillo 15.2.6-1 on CRAN: Several Updates

Tue, 21 Apr 2026 18:20:00 CDT

Armadillo is a powerful and expressive C++ template library for linear algebra and scientific computing. It aims towards a good balance between speed and ease of use, has a syntax deliberately close to Matlab, and is useful for algorithm development directly in C++, or quick conversion of research code into production environments. RcppArmadillo integrates this library with the R environment and language–and is widely used by (currently) 1263 other packages on CRAN, downloaded 45.7 million times (per the partial logs from the cloud mirrors of CRAN), and the CSDA paper (preprint / vignette) by Conrad and myself has been cited 683 times according to Google Scholar.

This versions updates to the 15.2.5 and 15.2.6 upstream Armadillo releases from, respectively, two and five days ago. The package has already been updated for Debian, and built for r2u. When we ran the reverse-dependency check for 15.2.5 at the end of last week, one package failed. I got in touch with the authors, filed an issue, poked some more, isolated the one line that caused an example to fail … and right then 15.2.6 came out fixing just that. It was after all an upstream issue. We used to ran these checks before Conrad made a release, he now skips this and hence needed a quick follow-up release. It can happen.

The other big change is that this R package release phases out the ‘dual support’ for both C++14 or newer (as in current Armadillo) along with a C++11 fallback for more slowly updating packages. I am happy to say that after over eight months of this managed transition (during which CRAN expulsed some laggard packages that were not moving in from C++11) we are now at all packages using C++14 or newer which is nice. And I will take this as an opportunity to stress that one can in fact manage a disruptive API change this way as we just demonstrated. Sadly, R Core does not seem to have gotten that message and rollout of this package was also still a little delayed because of the commotion created by the last minute API changes preceding the R 4.6.0 release later this week.

Smaller changes in the package are a switch in pdf vignette production to the Rcpp::asis() driver, and a higher-precision computation in rmultinom() (matching a change made in R-devel during last week in its use of Kahan summation). All detailed changes since the last CRAN release follow.

Changes in RcppArmadillo version 15.2.6-1 (2026-04-20)

Upgraded to Armadillo release 15.2.6 (Medium Roast Deluxe)

Ensure internally computed tolerances are not NaN

The rmultinom deploys 'Kahan summation' as R-devel does now.

Changes in RcppArmadillo version 15.2.5-1 [github-only] (2026-04-18)

Upgraded to Armadillo release 15.2.5 (Medium Roast Deluxe)

Fix for handling NaN elements in .is_zero()

Fix for handling NaN in tolerance and conformance checks

Faster handling of diagonal views and submatrices with one row>

Sunset the C++11 fallback of including Armadillo 14.6.3 (#504 closing #503)

The vignettes have refreshed bibliographies, and are now built using the Rcpp::asis vignette builder (#506)

One rmultinom test is skipped under R-devel which has switched to a higher precisions calc

Courtesy of my CRANberries, there is a diffstat report relative to previous release. More detailed information is on the RcppArmadillo page. Questions, comments etc should go to the rcpp-devel mailing list off the Rcpp R-Forge page.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. If you like this or other open-source work I do, you can sponsor me at GitHub. You can also sponsor my Tour de Shore 2026 ride in support of the Maywood Fine Arts Center.