Test environments Platform: Ubuntu 18.04.1 LTS using R version 3.4.4 (2018-03-30) x86_64-pc-linux-gnu (64-bit) Platform: Windows via Win-builder using R-release, currently R-3.6.1 using platform: x86_64-w64-mingw32 (64-bit) R CMD check results There were no ERRORs or WARNINGs or NOTEs.