[R] update.packages() after updating R version

[Rich Shepard]

   R-3.5.0 is installed here. When I tried to update installed packages
errors were reported when their dependencies were built under a prior
version of R.

   Reading ?update.packages() I did not see an option that would
automatically update dependences built under an earlier version of R. Is
there such an option that I missed?

   Alternatively, is there a function I can run that will rebuild all
installed packages after I upgrade R versions?

Regards,

Rich