[R] How to updating R to the newest version conveniently

[Yong Wang]

Dear R users
I have been using R for a while. However, I don't know what is the 
convenient way to update R to the newest version while keep all packages 
I previously downloaded and installed from CRAN, if updating all those 
packages the same will be even better.
for the time being, I reinstall all those package evrytime after updating 
the version.

Thank you.

best regards
yong