previously installed package retrieval feature is in beta mode and you may need to manually install back your packages after upgrading R version. Thanks God they are free :)
updateR is not currently on CRAN. To install it, you can use the devtools package:
install.packages("devtools")
devtools::install_github("AndreaCirilloAC/updateR")To update R, run updateR(admin_password = "PASSWORD"), where "PASSWORD" stands for your system password. The function will display the version that R has been updated to when it finishes.
No compatibility check is currently performed between your OS and the installed version of R.
To find out more on updateR, see the dedicated blog post: http://www.andreacirillo.com/2018/02/10/updater-package-update-r-version-with-a-function-on-mac-osx/