Test environments local OS X (High Sierra, 10.13.6) install, R 3.5.1 local ubuntu (18.04.1) install, R 3.5.1 ubuntu 14.04 (on travis-ci), R 3.5.0 win-builder (devel and release) R CMD check results 0 errors 0 warnings 0 note Reverse dependencies There are no reverse dependencies.