updating R with installed packages

found this very good instruction. keeping for future references-

"First, we need a location to install all our packages from now on. This can be any directory, and location of this directory should be indicated in ~/.Renviron file. Let's create that directory now:

mkdir ~/Rlibs

We created Rlibs directory in our home directory. Now, create the .Renviron file in your home directory and enter the following line and save the .Renviron file:

 R_LIBS=~/Rlibs

We can now start R and install any library. The libraries will be installed to ~/Rlibs, and when we update R, R will still look for libraries in ~/Rlibs directory so we don't need to re-install the libraries. However, we will need to update the libraries in ~/Rlibs directory to their most recent versions. All we need to do is to run update.packages() in R console, and the libraries will be updated."